[Music] hello and welcome to here tutoring in this video we're going to talk about when and how to use the answer choices for the act math test first let's just make sure we say that we are allowed to use the answer choices the act math test is not like a normal math test where we need to start from the beginning and work to the end to show all of our work in fact we shouldn't do that because our goal isn't to show anyone that we know how to do the question rather our goal for the AC math test is simply to get the right answer as quickly as possible using whatever method necessary and sometimes the best method to get the right answer is to just use the answer choices and plug them back into the question even if we know how to do the questions the right way this is because sometimes the right way to do the question will actually take a lot longer than just using the answer choice now let's talk about how and when to use the answer choices regarding the how the most efficient way to use the answer choices is to start with C since it will always be the choice that's right in the middle if c ends up being wrong then we only need to pick one more choice to find the right answer if c ends up being too big then we know the answer needs to be either A or B then we just need to pick either A or B to plug in if it's right then great if it's wrong then we know the answer is the other one likewise if c ends up being too small then we know the answer will be either D or E so we pick one of them the plug in if it's right great if it's wrong then we know the answer is the other one on the other hand if we just started with Choice a and worked forwards we might need to try four different choices if the answer is e instead of just two using this method where we start with C now let's try this with two examples first let's take a look at this question if 2 n + 1^ 2 - n - 5^ 2 equals 16 then what could be a value of n our choices are 1 2 4 5 and 6 for this question we should recognize that it would take quite a while to foil out the entire problem and find the roots so this will be a perfect question to use the answer choices four so let's start by trying Choice C which is four when we plug four in we end up getting 9^ 2 - -12 = 16 which simplifies the 81 - 1 = 16 which is 80 = 16 which doesn't work we see that 80 is too big so let's try one of the smaller choices let's try a by plugging one back into the original equation when we do this we end up getting 3^ s -4 = 16 which simplifies to 9 - 16 = 16 which simplifies to -7 = 16 which doesn't work either so now we know the answer needs to be between a and C or between 1 and four so we can just pick B at this point and move on but if we wanted to check this we would see that plugging two back into the equation gets us 5^2 - -32 = 16 which simplifies to 25 - 9 = 16 which simplifies the 16 equal 16 with this method of using the answers we will only need to try at almost two of the answer choices whereas if we started from the beginning we might need to try up to four choices now if we wanted to actually set this question up and solve it we would have had to distribute or foil out everything combine all the like terms get everything to one side so they equal zero and then find the roots probably using the quadratic formula which would have taken a lot longer using the answer choices was a much better option for this question now let's try one more example together let's take a look at this question in a bag of marbles 1/3 of the marbles are red 1/4 of the marbles are blue 1 six of the marbles are green and 21 marbles are yellow how many total marbles are in the bag our choices are 48 60 72 84 and 96 like with the last question we can figure out pretty quickly that this question will take a while to set up and solve and that using the answer choices will probably be quicker and easier so here's how we could use the answer choices let's start with C which is 72 if there are 72 marbles in the bag then 1/3 or 24 are red 1/4 or 18 are blue 1/ 16th or 12 are green and 21 are yellow this adds up to 75 marbles Which is higher than 72 so we know that 72 is too small which means we should try D or E for our next answer choice to use let's try D or 84 if there are 84 total marbles in the bag then 1/3 or 28 are red 1/4 or 21 are blue 1 16 or 14 are green and 21 are yellow this adds up to 84 which is what we were aiming for so our answer is d as you can see if we had started from a and moved forward we would have needed to try three answer choices instead of just two if we had wanted to set up and solve an equation for this question we would have done 1/3 x + 1/4 x + 16 x + 21 = x then we would have changed the fractions to common denominators to get 4 over 12x + 3 12x + 2 12x + 21 = x then we would have combined the like terms to get 92x + 21 = x which simplifies to 3 over 4x + 21 = x then we subtract 3 4X from both sides to get 21 = 1 4X and finally we multiply both both sides by four to get x = 84 which is our answer but that took a lot longer than just using the answer choices so the two examples that we just went through help give us an idea what kinds of questions would be good candidates for using the answer choices generally speaking the questions that we want to consider using this method for are ones we're setting up and solving the algebraic equation would take longer than just plugging in the answer choices in the next video we're going to talk about an act math strategy similar to this one which is substituting in random easy numbers into the question to figure out the answer thanks for watching and I hope to see you soon [Applause] [Music]