what is up my people this is Mr twoe creator of the TSI math crash course series and I am so excited to announce that TSI math crash course has been updated to reflect some of the newest Concepts and question types students are seeing tested on the tsia 2 math exam in this video I'm going to teach you the easiest and fastest way to solve a number of those question types so you can easily pass the new tsa2 math test with flying colors oh by the way if you like this video you definitely want to get access to the full version of the course just click the link in the description below to access access the full version in the meantime sit back relax and enjoy these tsia 2 math answer explanations all right welcome everybody to TSI math crash course this is uh day six the day six update really the update to the day six update for the tsa2 uh math test and uh we've got a student with us this is Bailey say hi to everybody please Bailey hello all right thank you Bailey I appreciate it so Bailey reached out to me um a few weeks ago and she had some questions that that she'd seen on some practice tests that she was kind of unsure about and uh and I want to go over some of those those questions with her today also there's some questions I've seen on some recent uh TSI tests um a couple Concepts I was a little bit surprised to see that don't appear on the practice tests and uh I really haven't seen anywhere else but I saw them on the actual test so I've kind of recreated some versions of those questions and uh and I want to go over those today a couple new Concepts uh like absolute value and like stuff with trapezoids and graphing a circle on the XY and and uh just some more complicated geometry and things so um I want to go over all those questions here on this day six update just so that everybody watching uh my videos has uh has a handle on the most recently released kinds of Concepts and question types that are tested on the tsa2 math test so let's jump right into the questions bayy we got a question up on the screen go and read question number one for us and we'll solve it together um which of the following could be the equation depicted on the graph okay okay yeah yeah now you've see did you see any questions like this on the TSI where they give you like some line or a parabola they're like What's the equation of the graph is this familiar yeah it is I definitely something and you worked your way through you know the the course as well and there's lots of questions like this on the practice test now I generally recommend uh you know just plug in the points from the XY AIS right like even if it's a parabola or a line right you I mean you can kind of like think in terms of yal MX plus b if it's a line if you're really comfortable with that but you I always tell students just pick values from the XY AIS and then plug those into the equations and that's just like the easiest most straightforward way to solve it generally and we can do that here as well in this question now what's kind of funky about this if you look at some of the answer choices here in this question look at answer Choice A and B do you see those funky lines like around x- one and X-2 do you see that yes yeah have you seen that notation before have you seen those funky lines those are called absolute value lines or absolute value bars yes okay are you do you know what absolute value mean means are you familiar with that um isn't it like they're the same value outside of the lines like well let's or let's talk about it because I do I have updated my uh TSI math cheat sheet as well to reflect absolute value because they're testing on it now on the TSI so let's go to that cheat sheet so open that up you should have access to that I'm going to zoom in a little bit here and then this is toward the end of the cheat sheet this is basic concept I I've kind of added this on absolute value so kind of scroll down it's like the second to last page and let me know when you're there all right I'm here all right great go and read uh that bullet point for absolute value please calculate what's inside the bars if it's positive keep it positive if it's negative make it positive okay good and i' I've got an example there of the absolute value of 3 minus 5 the absolute value of 3us 5 that's how you'd read that and uh and so when you see absolute value real simply you can kind of deal with it like parenthesis kind of you know calculate what's inside the bars and by the the way what's 3 minus 5 Bailey what does that equal uh it's negative -2 yeah it's negative2 okay and then if it's positive you know once you've calculate what's in the bars you keep it positive but if it's negative you make it positive okay so 3 - 5 like you said is negative -2 it is but because it's inside those absolute value bars you just got to make it positive and that's why the absolute value of 3 - 5 is two positive two does that make some sense yes okay if it were parentheses not those straight bars then it would be two of course but with those straight lines just make make sure it's positive basically calculate what's inside the bars whatever comes out of that is going to have to be positive does that make some sense yes okay great so let's go back to the question up on the Whiteboard okay and um and you know we could we could think in terms like I I said earlier of sort of of of of graphing if you're familiar with like graphing lines maybe you could graph C and D most students aren't super familiar with graphing absolute value and I'm not even super comfortable with it I'm not so let's just take points from the xyx let's just start with this point right here sort of at the bottom of of that vshape that appears on the graph okay what is that point right there Bailey do you do you know how to describe that point in terms of X and Y yeah it's it's one two Well's actually not it's actually not one comma two this is a common mistake students make um so keep in mind that when you see an ordered pair it's going to be X comma y the X comes first yeah and if you forget no it's super common mistake and I'm sometimes too um just think in terms of alphabetical order right like X comes before y in the alphabet right like that's good enough and and I recommend thinking those terms so so what's the x value at that point it's not one what's the x value it's two the x value is two and what's the yv value oops uh it's one it's one absolutely so that's the0 2 comma one does that make sense yes okay great so we can test the answer choice just by taking that point 2 comma 1 and plugging it into the answer choices calculating those and the right answer has to give us a true statement okay now if we get multiple true statements then we'll just plug in another set of points that happens sometimes um you know but I think two two comma one is going to work here to give us the answer so let's plug that point in two comma 1 remember that's X comma y plug that into answer Choice a and let's just see what happens okay just find a a spot on the Whiteboard and let's calculate that yes okay can I write it down here is that all right anywhere yeah anywhere you got space okay so you want to plug in the one for the Y as well yeah we plug in the one for the Y and the two for the X and I like when when you're doing absolute value bars I like making them like real like long like obnoxiously long just so they don't like because otherwise it could look like 12 you know what I'm saying yeah like I get that yeah okay but you're doing great okay sorry I didn't put eal Cent yeah I got you I got you so would it be like that yeah yeah so 2 - one is one positive one what's the absolute value uh and I'm going to zoom out just a little bit here all right so yeah the absolute value of one is just one right here so you get 1 plus two and that is three so you get one equals three so what do you think about answer Choice a uh no probably not not if last one does not equal three that is correct all right so let's plug in answer Choice B I'll clear some space for you here on the Whiteboard and um oops clear that all right thank you yeah you're welcome all right okay looking good looking good yeah so we get a true statement here right one equals one and the absolute value of zero for anybody watching the court isn't isn't uh certain about that the absolute value Z is just zero it is so um so we get a true statement there for answer Choice B let's keep it does that make sense Bailey yes okay great let's plug into answer Choice uh C and let's see what happens space my handwriting is so bad with you're good you're good you're good I can read it I can read it all right true statement no clearly not right so answer Choice C is gone and let's plug into answer Choice uh d as well clear the space okay yeah not not a true statement very simple all right so uh we can confirm it's answer Choice B so I have seen uh question like this on the TSI with absolute value and just be aware if You' seen an absolute value question it's always going to graph as like a vshape basically so just recognizing that you can sort of like narrow it down to a and b but I said just always plug in the points and just kind of be aware of how absolute value Works remember just calculate what's inside the bars if it's positive you keep it positive if it's negative you make it positive a lot of students kind of misinterpret they think you you flip the sign and that's only true it's negative that's the only time you flip the sign but if you get something positive inside the absolute value bars you don't make it negative doesn't work that way if it's POS keepi if it's negative make it positive and you got a question like that did you see one like this on on on the TSI that you took recently or maybe not um I didn't see one with absolute value or anything but it's like definitely like depict the equation sort of thing very yeah and that applies to a lot of different kinds of graphs that they could give you but I've seen it on recent tests so there's a good chance you could see it as well so any questions about this before we move on uh no thank you great all right let's move on the next question aha this is a factoring question I'm zoom in a little bit and then go and read question number two when you see that up on the screen which of the following is a factor of the polinomial above o what are we solving for here do you have any idea um well I know how to factor it but like I don't know what it's asking like specifically like what your final ANS is of all of it yeah if if you're familiar with factoring some students are I hate factoring by the way most students I work with as well like really struggle with fact it is it's a pain in the butt operation it really is um but like there's a way to like basically break this polinomial break it up into like two sets of terms in parentheses basically right that you'd multiply together to get that polinomial that's underlying green there's a way to do that um I generally don't recommend doing it's just so easy to mess up and it's such a specific operation um there's a way to plug in values on these factoring questions I they asking about the factors of some polomia there's always a way to plug in values that's what we're we're going to do here but first let's talk about what a factor means let's start there Bailey do you know do you know what a factor is like the definition of a factor or maybe not so much I don't know what the definition of it is let's talk about it because I think it's really helpful to understand what that is here to to solve this question look at the number uh the number 12 let's start there number 12 the number 12 has a variety of factors that is to say a factor is a number that you multiply with another number to get another number okay so like there's some numbers that you could multiply together that give you 12 okay what are some of the numbers that you could multiply together to give you 12 like four time three yeah four time three so both four and three are factors of 12 does that make sense but there's there's more there's more factors of 12 what other factors are there more num M together one and 12 one and 12 absolutely because 1 time 12 is 12 so those are also Factor there's more there's a lot more yeah what else um hold on thinking yeah yeah let me help you out a little bit you could do six six and two exactly six and two are factors and then get this also the negative versions of those numbers are also factors so like4 is a fa is a factor because you multi * neg3 I know right there's a ton of factors right yeah1 and -12 right I mean this get it can get involved -6 and2 are also factors I think that's it for the factors of 12 but basically some numbers you you multiply together to get another number those are the factors does that make some sense yes yeah and that's sort of easier to wrap your head around I think when you're dealing with like actual numbers that's what we're doing with this question we're tur it into into arithmetic but there are also some like terms algebraic terms with like you know X that we can multiply together to get the polinomial in the question but it's the same idea right terms that you multiply together to get another term does that make some sense okay okay yes all right so here's what we're going to do we're going to plug in a value for x into this expression here in the question okay I'm going to start with x equals one we could start with zero uh and that's usually you know ones and zeros are great you you worked your way through the course you know I love ones and zeros right but I know if I plug in a zero here I'm not gonna be able to get rid of any the answer choices just because I was I on this question previously here before but uh we can start getting rid of some with with one and I think when we plug in a two for sure we're going to be able to get rid of all the wrong ones but but um we're going to plug in a one for X into the the expression in the question we're going to find what that equals we're going to get like a number when we plug in a one for X okay and then we're going to plug that same value for x into the answer choices and then we'll see which of those answer choices are factors of the number we got when we plugged a one into the expression does that make a little bit of sense yes it does okay good good I think it'll be really really clear as we as we work through this so let me clear some space here on the Whiteboard and then um let me see you plug in a one for X into the expression in the question now be real careful when you're plugging in here I really recommend uh using parentheses when you're plugging in but just pluging a 1 forx into that 3x2 plus 25x minus 18 let's just see what happens looking good looking good great I want to make it really clear anybody watching the recording here that means one squared right there one squared we're not squaring the three we're just squaring the one that's 3 * 1 it's kind of a common mistake students make a lot of students think this expression right here equals nine that doesn't equal nine that's just three looking good looking good uh now hold on I'm gonna stop you real quick I might yeah so what is let's let's um what's 25 minus 18 um it's seven that should be seven positive seven does that make some sense oh my bad yeah that's right I mix up negatives boy it happens a lot um that's right yeah so that should be 3 plus 7 great yeah so the expression in the question equals 10 when X is one does that make some sense yes okay great all right so let's plug in that one into the answer choices as well and let's see which answer Choice gives us a factor of 10 or which answer choices we might get some multiple answer choices here but let's plug in answer Choice a what do we get you might even be able to do this mentally what do we get uh when we plug in a one for X into answer Choice a negative negative eight yeah we get negative eight is that a factor of 10 no no that is not a factor of 10 so uh answer Choice a is gone does that make sense so far yes yeah because you can't multiply negative eight by some whole number and get 10 it's just not going to happen all right so uh a gone what about answer Choice B what do we get uh four we get four positive four h is that a factor of 10 no it's not right because you can't multiply four times some whole number and get 10 it's not a factor so B is gone as well this is working out well uh let's try answer Choice C what do we get let me see you plug this in yeah yep 3 minus two what does that give us uh one so uh yeah that gives us one so is that a factor of 10 technically yes yeah yeah it is not just technically it is a fact right because you can multiply 1 time 10 and get 10 so C could be right let's keep it and let's plug in answer Choice D and for is not a yeah you got four four not oh great so we by plugging in a one we could get rid of all the wrong answers and we can confirm its answer Choice C W I thought we have to plug in another number we didn't need to there one just worked great does that question make some sense now yeah it's a lot easier than factoring it's a lot easier than factoring it's a lot easier than factoring I mean we could go over those operations I I have zero desire to it's uh every factoring question I've seen on the TSI you can turn into arithmetic and that's the case here okay so any questions about that yeah okay do be aware sometimes you might get multiple answer choices that give you a true statement right again if we plugged in a zero I just kind of want to take a look at this real quick uh if we plugged in a zero for X into the expression in the question what would we get oh we' get Negative 18 if we plugged in a zero for X do you see why that would be the case if x were zero yeah if x is zero we get 18 because that becomes zero basically that becomes zero we're left with just negative 18 right make sense yeah and then um if you look you plugg a zero to the answer choices then you'd get let's see a would give you9 that is a factor of ne8 doeses that make sense yes yeah uh answer B would give you three also a factor of 18 because you multiply 3 * -6 and get 18 does that make sense yes yeah C would give you -2 also a factor and D would give you one right so like that's why like and that happens sometimes that's okay remember this is an untimed test you got all the time in the world essentially um so if you got to plug in multiple values you know don't hesitate to do that beware that's going to happen sometimes so don't just stop when you see something that looks good make sure you're testing all the answer choices and if you got to plug in multiple values uh that's totally cool totally normal does that make sense okay yes but here it is it is answer Choice C we can confirm that by plugging in the one for X all right let's take a look at some the next questions we're talking about percents coming up and some percent increase and decrease I've seen some of those questions popping up number three is kind of a real straightforward question um but I want to go over it just because I want I want to understand how percents work before we get into some of the more complicated questions on percent increase and decrease and kind of review that uh go and read question number three for us please a farmer plants 400 seeds in his garden which of the 85% sprouted how many seeds sprouted yeah it says of which 85% sprouted so of those 400 85% sprouted does that question make some sense yes okay so I I just want to kind of talk about this from a logical perspective right off the bat before we do an operation we will get into the operations here but um you know we're talking about some percentage of 400 that sprouted is the number of seeds that sprouted is that going to be bigger than 400 or is that going to be less than 400 uh less it's got to be less than 400 right I mean 100% of 400 would be 400 but anything less than 100% it's going to be a number smaller than 400 does that make some sense yes yeah so like right off the bat we can get rid of at least one answer choice that doesn't make any sense what answer Choice can we get rid of D yeah we can get rid of d right because that's just bigger than than 400 and that doesn't make any sense so just you can think in those terms and start getting rid of some bad answer choices I just kind of want to point that out um okay now um notice by the way where they get an Choice D from right this is like that's just you're adding yeah right like they love doing that be you know this is I call this number slapping students do this a lot where they're like oh I see a 400 and an 85 like I'll just add those together I'll just subtract those together right you know it's like it doesn't you know I mean no don't don't do that you're better off like just feeling your way through it and really understand the question then by just doing like a random operation with numbers so okay let's talk about the operation here because we can we can solve this pretty easily if you understand what percents mean do you understand what 85% means Bailey I mean it's a I mean it's like the amount of the initial amount that I guess succeeded in a way like I couldn't tell you the definition but I know how to yeah yeah most you've got like an 85% on a test you're like okay I got most of them right I did all right got like a be you know you kind of know what it means now there's a definition of percent and I think I probably addressed this like way back on day one of the course but uh percent means per 100 or out of a 100 I think it's really helpful to understand that like Cent means 100 that's it's a Latin for a 100 bayy how many years are there in a century do you know it's not uh no no that's right TR help you out that's okay there's a hundred years in a century there's a 100 years in a century how about this how many cents are there in a dollar how about that uh 100 100 cents right that's where it comes from there's 100 cents in a dollar so it's a scent I did not know that yeah right isn't that kind of cool yeah so 100 years in a cent a decade has has 10 years yeah some students get decades and centuries mixed but Deca means 10 right you actually see that sometimes in math every time about like a dealer or something like that but uh but anyway but so 85% means 85 out of 100 that's what it means okay literally right does that make sense why yes okay great so 85% is 85 out 100 now if you got a calculator what you should have on a question like this on the TSI and I don't know if you've got a calculator you with you right now or you've got like an iPhone or something like that I want you to punch that into the calculator punch in 85 divided by 100 and tell me what you get you'll get a decimal that's the same as 85% yeah you get 085 you get 085 so I really want you to understand this 85% equals 085 it is 085 the same thing so if you ever want to find 85% of something all you got to do is just multiply the original value by 085 and then you'll find 85% of it and that's all the questions asking us here we're just finding 85% of two of 400 we'll multiply 400 time 085 do that in your calculator real quick tell me what you get we should get the right answer it's 340 340 answer Choice C does that make some sense yes yeah yeah if you have if you want to find like I don't know like 15% of something what would you multiply by let's just talk about it um you would multiply by 15% 100 yeah so it's 15 divided by 100 what is 15 divided by 100 punch in your calculator real quick it's 15 yeah5 0.15 right so if you want to find 15% of something multiply by 0.15 if you want to find 50% of something right it's just half of it multiply by 0. five 050 if you want to find 60% of something just multiply by 6 you want to find 65% of something just multiply by 65 does that make sense yes you see a question like this where they're like hey what percentage of this value or what's the percentage of this value um or what value would be a percentage of this value then just multiply by that percent and that's it questions about that ifes that make some sense that makes sense okay it's a pretty straightforward question I have seen some of these um on the practice tests that are that are this simple um you know I wouldn't expect to see this maybe on the first set of 20 maybe on the on the diagnostic section if you end up with the diagnostic section you don't pass that first set of 20 but I still want you to know how it works cuz you know so I have seen some questions like this you've got to like draw out some information on a chart I think on the most recently released practice test it's there's like a percent increase question or like a fifth increase or something like that but it works the same way yeah um you know and uh um and but you have to know how percents work and what they mean to be able to get the percent increase and decrease questions which are a little more complicated those are coming up right now any questions about this before we move on no okay great but just know what percent means and then then you can you can navigate it all right let's talk about percent increase all right go and read question number four when you see on the screen Bailey uh a company with 140 employees estimates that the next year of employees will increase by 35% next year um according to the estimate how many people will be employed by the company next year what what are we solving for here Bailey um how many people will be employed in the company next year how many will be employed by the company next year absolutely and uh you know if we just look at the question carefully we know that number of employees is going to increase by 35% next year okay so are we talking about more than 140 employees or less than 140 employees next year uh more there got to be more than 140 right and like just knowing that by the way we can get rid of two answer choices that are just ridiculous if you understand what that means what what an can we get rid of right off the bat uh A and B A and B are gone absolutely and I think where where Anice a comes from I think that's like 35% of 140 would be 49 does that make some sense it's just that I think it seems right I that's where where that comes from um so be careful right don't just see two numbers and be like Oh 35% of 140 it's like that's not what it's saying right it's saying it's going to increase by 35% so be careful there it's going to be some number bigger than 140 there's no way around it so it's either C or D okay let's talk about calculating this what's what this is going to be if we increase it by 35% do you have any idea how to increase 140 by 35% do you know how to do that um I mean my guess would be take 35% added to it yeah you can do that it's sort of a two-step way let's start there okay if you find 30% of one or 35% of 140 we'll find out what that is and then we can add it to the 140 and that'll give us a 35% increase does that make sense let's do that real quick so really it's just 140 times what what do we multiply by 35 0.35 right yep multiply by 035 or 0.35 same thing what does that give us uh 49 that gives us 49 right which is where answer Choice a comes from a lot of students would pick answer Choice a here on this question you can see why right they just do a calculation oh 49 sweet but that's not the number of employees right we've got to add that to the original value which which is what so that' be 49 plus 140 uh 140 yeah which is uh 189 189 answer Choice D does that make some sense yes okay so that totally works sort of that two-step method right of like find the percent and then add it back to the original value that totally works let me show you another way to do it that I prefer I'll show you why here in just in just a minute especially if we're talking about a percent increase or percent decrease over time you have to know this onestep method let me show you how this works instead of multiplying by 035 and then adding it back you can just take the original value in this case 140 and instead of multiplying by 035 just multiply by 1.35 1.35 okay take a look at that expression real quick let me show you why this works first of all what would 140 * 1 be 140 140 right so this is going to be at least 140 fact it's going to be a little bit bigger than 140 because we're multipli by something a little bit bigger than one does that make sense why we know this is going to be bigger than one yeah yeah but it's not just uh you know it is a little bit bigger than than one it's exactly 35% bigger than one because 0.35 means 35% so if we multiply 140 time 1.35 that automatically in one step increases 140 by 35% does that make some sense it does yeah yeah punch that in your calculator real quick let's just make sure that the math works here I think it should but go ahead and multiply 140 189 yeah yeah there you go it's 189 right in one step okay now this is important because sometimes they're asking you to like structure expressions like over time something's increasing by like 35% every year it's going to look like like that you know for if T is the number of years and um and and so you do have to know sort of that one step way of doing things we've got a percent decrease come question coming up next where it is over time so I really recommend getting getting familiar with that one-step method if it's percent increase you should be multiplying by something bigger than one and if it's percent decrease you should be multiply by something less than one does that make some sense okay yes okay now let's say let's say you want to increase something by 25% what would you multiply by um 1.25 1.25 absolutely what if you want to multiply or increase something by 30% should you multiply by 130 130 absolutely what if you want to multiply or increase the by 50% what should you multiply by 150 yeah 1.5 or 150 what if you want to increase thean by 90% what should you multiply by 1.90 1.90 absolutely questions about that or does that make sense that makes sense okay great great all right this one gets a a little bit trickier here this is a percent decrease over time question fun oh yeah oh yeah have have you seen any of these on on practice test yeah yeah they like these right but once you have the foundation of sort of the the concepts that we we worked on in the early questions this this is going to make perfect sense okay go and read on number five for us please a certain stock initially worth $200 Los 20% of its value every year which of the following Expressions represents the value of stock after some number of years t o what are we solving for here Bailey um the value of the stock after some years the yep the value of the stock after some number of years in this case that's that's T is a number of years okay this is a tough question for a lot of students because like these Expressions all look pretty similar and it's just like man I don't know how to structure that stuff like this is just it's just it's just tough it's not obvious looking at the answer choices what the writing answer is it's just not obvious okay one place to start and this is where you I mean good Heavens you've worked way through the course you know I love plugging in values that's a place to start it's a place to start here right we can plug in some values for T and like see what's reasonable that's a great place to start right even if you don't know how to structure it okay we're going to talk about that as well I want you to know the operations too but let's start just by plugging in values and doing like basic logic and estimation okay so like let's start with a one for T right like let's see how much is going to be how much the stock is going to be worth after one year does that make some sense yes okay now before we calculate this we're going to plug in you know make make t equal one we'll plug that into the answer choices before we do that I mean could you estimate how much the stock is going to be worth after a year like I just want to see if we can sort of anticipate what the right answer Choice might look like what do you think how much gonna be left after one year like after it loses the 20% yeah after it loses the 20% so that would be yeah after one year like you don't have to calculate here but it's gonna be a little right it's gonna be a little bit less than 200 yes it's G to be I I don't know like 60 something like like 160 yeah I think it might exactly be 160 right like that's really reasonable right that feels rough right not it's not like it be $100 that'd be like going down 50% right so but it's going to be a little bit less than than 200 okay so plug in a one for T into answer Choice a okay I I'll just write it out for the sake of here so that's going to be 200 time8 to the power of one now what is something to the power of one what does that mean by the way it's it's just multiplying it by itself yeah just just by itself basically so yeah it's 08 once one time right so yeah so anything the power of one is itself so that's just 200 times8 does that make sense yes yeah punch that in your calculator tell me what you get what's 200 * 08 uh it's 160 it's 160 which is nice right I mean that's like kind of what we anticipated now hold on hold on I mean don't we just talked about this earlier in our previous question don't just stop when you see something that looks good right especially when you're plugin in values they're designing answer choices knowing that students are going to use this method it's the most powerful and useful method there is on all these standardized tests so you got to test them all but that looks pretty good right now we'll keep answer Choice a does that make sense yes let's plug into answer Choice B so that's going to be you know it's going to be the same or similar here it's going to be 200 time2 to the power of one which is 200 time2 what ises that equal right uh 40 40 do you think that's the value of the stock after one year no no way that's way too small is that clear Bailey yes and it's so funny because I'm guessing one of the most commonly picked answer choices on a question like this is g to be answer Choice B maybe that's the first one I thought it was yes maybe especially for students that are familiar with percentages because they see 20 % in the question and they're like oh sweet 20% that's point two must be answer Choice b or d right and it's a totally reasonable thing to think but when you start plugging in values and thinking in concrete terms with it with the numbers you get a ridiculous value for answer Choice B doesn't make sense it's not B we can get rid of it does that make sense Bailey yeah I'm in stats so that's what I initially thought yeah yeah right and and and it's It's tricky because they're developing these an choices based on common misconceptions about math um you know I get it you know but uh but just make sure you know as as much as you can plug in values and think in concrete terms you avoid a lot of the pitfalls okay let's plug in answer Choice C and so that's going to be 08 time 20 to the power of one that's just 08 time 200 what's that equal it also gives you 160 also 160 right it's the same calculation as 200 time 8 it's the same thing so we got to keep B for right now okay let's try answer Choice D what does that give us2 200 um it's the same as B the same same calculation right it's going to give us 40 so that's ridiculous that doesn't work that's way too small questions about that or does that make some sense that makes sense okay okay so uh look we've plugged into some values we got rid of two of the answer choices but we we didn't confirm the right answer yet what did we do Bailey what did we do uh can we plug in another value plug in another value you know the drill absolutely right so let's do it let's just plug in a two and let's see what happens okay now it's going to we're done with b and d we know that doesn't work um uh for one so it's not going to work for it doesn't matter if you know like it's the B and D are just gone yeah so let's plug in an A so now we're making t equal 2 so you got to be careful here we're raising 08 to the power of two okay right so8 time so it's 8 time Point yeah exactly B Be really careful here guys you know anybody watching the recording you're not squaring the 200 you're just squaring the 08 that's 8 squared or 08 time8 same thing and then you multiply it by 200 so what does that give us yes 200 time 64 perfect this gives us 128 128 yeah great you got it Go and write it out great okay so does that seem reasonable could that be the value of the stock after two years when this thing is losing 20% every year could that be after two years yeah yeah after two years that's really reasonable right because if it goes down to 160 after one year then another 20% decrease will take us down a little bit less than 160 that's reasonable keep answer Choice a okay let's plug into answer Choice C now answer Choice C remember we're plugging in that two for T so now we're squaring the 200 and already that's looking pretty suspicious if you know what it means to square something right right but like let's calculate it I want to show you why it doesn't probably work which I oh that's a big number that's 200 times 200 yes whoa whoa whoa okay whoa that's a big number do you think that's the value of the sock after two years if it's losing 20% of its value a hard pass yeah yeah probably probably not for uh for that answer choice so so that is uh answer Choice C is gone we can confirm it's answer Choice a which it is does that make some sense yes okay good I love plugging in valys good Heavens it works works beautifully there let's talk about sort of the operation now though okay um if we wanted to calculate a 20% decrease okay I'm going to clear some space here on the Whiteboard give me just a second do you mind help me clear this i' I've got access to my but not yours yet C all the stuff there we go okay good okay so if you want to decrease something by 20% okay you you could do that whole thing where you calculate 20% of something and then and then instead of adding this case we'd subtract it right so let's do that right if if if uh let's say after one year right this stock is losing 20% of its value it would just be 200 time .2 right that's 20% of 200 what does that give us by the way it gives us 40 gives us 40 and then you subtract that from 200 and it gives you what giv you 160 gives you 160 right which is uh what we got when we plugged in a one for t to answer Choice a and answer Choice C but that also just feels reasonable right okay it's originally 200 bucks but it goes down 20% something a little less than 200 160 works perfectly there so the decrease if we if we multiply 200 time 20% or 02 we'll calculate the decrease so then you got to subtract that decrease in the original value to get what you're left with does that make some sense yes okay so but a better way to do it if you're you can do it in one step if you're decreasing something by 20% how much is left if it's going down by 20% how much what percentage is left if it goes down by 20% 80% 80% so instead of calculating 20% subtracting it just find 80% of 200 and actually makes uh-huh uh-huh so so what do you multiply 200 by to find 80% of it uh 08 uh not 0 Z that would be 8% interesting sorry 08 Point 0.8 or0 eight yeah yeah if it's going down by 20% that means there's only 80% left every year that goes by and that's 160 yes and that gives you 160 right and then depending on what T is like little after two years it's basically it's going to be another 20% decrease cuz you're multiplying by 08 again if T is two or if T is three you're multiplying by 08 three times basically you're dropping it down 20% three times if you're multiply by 0 eight three times does that make sense yes and that's why the right answer is answer Choice a okay so if you kind of understand kind of the the structure of that if if you want to decrease something by 25% let's say what should you multiply by if you want to decrease it by 25% uh if you want to decrease it by 25 wait say that again yeah if you want to decrease something by 25% it's going down 25% what should you multiply by um you should multiply it by 75 75% or0 75 yeah yeah yeah what if you want to decrease something by 30% what should you multiply by uh 70 70 yeah 70% or0 7 it's the same thing yeah what if you want to decrease something by 40% what should you multiply by UH 60 60% or6 yeah what if you want to decrease something by 60% what should you multiply by 40 40% or4 exactly does that make sense yes okay so you can kind of think in those terms if you're familiar with how to structure a percent decrease question and we talk a little bit about percent increase in the last question as well or or just plug in the values as well you can avoid a lot of the traps you've got some options but I want to show you both ways of thinking about it your best bet here really is probably plugg in the values right because then you don't have to think about how to structure it exactly but be aware that the percent increase or decrease is always going to be the term like in parentheses right so if you're seeing you're multiplying by 08 in parentheses you know raised to some power that signifies a 20% decrease if you're multiplying by 0.2 in parenthesis that's going to signify an 80% decrease does that make sense yes that does yeah and if you're mul by 200 good Heavens that's a massive increase 2,000% or 20,000 it's not even not happen to man not Happ here questions about this uh no okay good have you seen any questions like this on on the the test you took on some of the practice tests yes they have a lot of the decreasing and increasing Valu y yeah yeah so maybe start with pluging in values but um but uh you can kind of confirm that if you understand how to structure it as well so let's take a look at some geometry questions now that they're testing on uh on the TSI all right