good day Legends welcome to techmath I'm Josh by the end of this video you'll be able to work out multiplication problems just like these ones right here in your head and I reckon you'll be able to do them in under 4 seconds let me know in the comments how you go with this this trick is the third in a series looking at instant Mental Math where truly nobody's even going to question your Genius anymore there is a link in the description that has a playlist for these videos so let's have a look at an example of this particular trick we'll start with this one here 20 3 multipli by 24 something nice and easy to start off with now this particular trick what you're going to notice about both of these numbers we're multiplying is they both start with the same 10 value in this case they're both numbers in their 20s for this trick to work it's important for that to happen so the way this trick works is as follows the first thing we do is we look at the units here we have for 23 three for the units and for 24 we have four the first thing we do to get the first part our answer is we add either 3 to 24 or 4 to 23 and when we do that we get the following 3 + 24 is equal to 27 now what we do is we multiply it by this 10 value right here either one so 27 multiplied 2 is 54 now this is the 10 part of our answer so we multiply this by 10 54 becomes 540 to this we add pretty simple we multiply through 3 * 4 3 * 4 is equal to 12 and we add those together we will have our answer 540 + 12 we have the answer of 552 hey pretty simple right nice and easy fast trick like I said you should be able to do this in under 4 seconds maybe 5 seconds for you okay by the way if you like this trick remember hit the like button and subscribe so those steps once again first thing this works for numbers that have the same 10 value like we have the 20s here we look at the units and then we have either 23 + 4 or 24 + 3 which equal 27 and now multiply by that 10 value 27 * 2 is 54 make that a 10 540 and then we just multiply those two units together 3 * 4 we add that on we've got our answer seems like a few steps don't worry we'll go through a few examples and I'll tell you what I want to see how fast you're going to be doing these so we'll look at those examples that I showed you at the start of this video we had 33 * by 39 74 * by 78 58 * 52 and 108 multiply by 112 now you might even notice on one of these there is another trick you can use that we looked at in a previous video I'll show you that as we come along so what about you pause these and give this a go let me know all right so what about I run through this answers now so we have 33 multiplied by 39 both numbers in their 30s the units are 3 and 9 respectively so the first step 33 + 9 or 39 + 3 the same answer is going to give us 42 and we multiply this by 3 so we multiply 42 by 3 we get the answer of 126 as I said before this is a 10 number so I put a zero on the end of that let's keep moving to this we're going to add well 3 * 9 3 * 9 is equal to 27 we add these together and we get our answer we have 1,287 is all you got well it's the correct answer how fast did you do that in well let's have a look at the next one we have 74 multiplied by 78 once again numbers now in their 70s so we have the units of four and 8 respectively 74 + 8 is equal to 82 okay 82 Now multip by 7 or 78 of 56 and we got 14 so we have 574 this is a 10 number we put a zero on the end to this we're going to add well 4 * 8 is 32 all right you get this nice simple answer of 5,772 all right did you go did you get two for two so far I hope so so to the third example we have 58 multili by 52 now what you might notice here if you're really been watching those other videos that I've been making on this is that there is a trick we can use for this where you can work this out instantly so check out the link in the description you'll be looking at video number one but I'm going to go through right now how you work it out using this particular technique so we have the units of 8 and 2 so first off we have 58 + 2 this is equal to 60 hey nice and easy right 60 multi by 5 here is 300 this is a tens number so it's going to become 3,000 and to this we're going to add well we have 8 * 2 which is 16 well this answer is probably the easiest all so far this is 3,6 so you definitely should have been able to do that one in under 4 seconds yeah so to the last example we have 108 multiplied by 112 now you're going to notice here straight away we're moved into some really big numbers we're in the hundreds and the T numbers are not the same we can make a bit of an adjustment what we do is we're going to use a unit of 8 for 108 and 12 for 112 and we're going to be using the 10 value of 10 yeah 10 10 are 100 let's just do the same thing here so 108 + 12 is going to be 120 so 120 * 10 is 1,200 and this is a 10 number that becomes 12,000 to that we're going to add well 8 * 12 which is 96 so we add these together we get our answer of 12,096 anyway that is the trick on how to multiply numbers that start with the same tens well like I said about 4 5 seconds but like I said let me know in the comments how you went with this how fast are you doing it maybe go through a few more examples let me know how you go so if you wish to know more of these math tricks that we've done so far or even new ones that are coming along if you are in the future and I've already put those videos up check out the link in the description there was a playlist big shout out to my if you want to support the techmath channel also check out a link in the description there you go thank you for watching and I will see you next time with the next math trick bye