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Current time:0:00Total duration:15:27

Video transcript

at this point I think you know a little bit about what multiplication is we're a multiplication we're going to do in this video is to give you just a ton of more practice and start you on your memorization of the multiplication tables and if you watch enough Khan Academy videos and hopefully you will in the future you'll realize that I'm normally not a big fan of memorization but the one thing about multiplications if you memorize your multiplication tables that will start to do in this video it'll pay huge benefits the rest of your life so I promise you do it now you'll never forget it and and the rest of your life everything will be well I don't want to make false promises to you but they'll be better than if you didn't memorize your multiplication tables so what are the multiplication tables well that's just all of the different numbers times each other so let's actually do a little bit of review so if I say what is 2 times 1/2 times 1 that is equal to 2 plus itself one time so this is equal to just two all right that's two plus it's up one time I don't have to say plus anything there's only one two there I could also write this as 1 plus itself two times so that's also one plus one well that also equals to fair enough so two times one is two and if you watch the last video what's 2 times 0 that's 0 so you don't have to memorize your 0 multiplication tables because everything times 0 is 0 or 0 times anything is 0 so let's see what's 2 times 2 2 times 2 well this is equal to we're going to add 2 to itself two times so that's 2 plus 2 and there's only way to do that I could say take this 2 and add it to itself two times but it's the same thing it was 2 plus 2 that's equal to 4 what's 2 times 3 2 times 3 is equal to 2 plus 2 plus 2 it can also be equal to 3 plus 3 right we learned in the previous video this statement can be written either of these ways and either case what's it equal to well 3 plus 3 is the same thing as 2 plus 2 plus 2 and that's equal to six all right now what is two times four two times four well that's equal to two plus two plus two plus two and notice it's exactly what two times three was two times three was that I have that here but now I'm just adding another two to it so if we're too lazy to sit here in nano 2 plus 2 is 4 4 plus 2 is 6 instead of doing that we could say hey look we already know that this thing over here this was 6 we've figured it out in the previous line right there we figured out this is 6 so we could just say oh 2 times 4 is going to be 2 more than that which is equal to 8 and you should hopefully see that pattern as we go from 2 times 1 to 2 times 2 to 2 times 3 what's happening how much are we going up by 2 from 2 to 4 we're going plus 2 from 4 to 6 we're going plus 2 and then from 6 to 8 we're going plus 2 so you could figure out what 2 times 5 is even without doing the addition 2 times 5 is equal to 2 plus 2 plus 2 plus 2 plus 2 could also be written as 5 plus 5 2 times 4 could've been written as 4 plus 4 as well now what's that equal to we could add all of these up or we could add these two up or we could just say it's going to be 2 more than 2 times 4 so it's going to be 10 I'll just can all finish the 2 times tables and I think you see all of the patterns that emerge from it so 2 times 6 that's going to be 2 plus itself 6 times C 1 2 3 4 5 6 which would also be equal to 6 plus itself 2 times this could be interpreted either way and that's going to be equal to 12 once again 2 more than 2 times 5 all right because we're going to we're adding 2 to itself one more time so it's going to be 2 more let's keep going so 2 times 7 2 times 7 is equal to well instead of I could write 2 plus 2 plus 2 plus 2 this is getting tiring 2+2 is that 7 1 2 3 4 5 6 7 and that's the same thing as 7 plus 7 which you may or may not know is equal to 14 but this you could just say hey that's going to be 2 more than 12 so 12 plus 1 plus 2 is 12 plus 1 is 13 12 plus 2 is 14 all right let's just keep going 2 times 8 2 times 8 I could do all of this business here where I add the twos or I could say look it's just going to be 2 more than 2 times 7 so I could say it's going to be 14 plus 2 I'm just adding 2 to that one so I could say it's sixteen or I could also say that's 8 plus 8 8 plus 8 that's also 16 I could have done all the twos out but if you'd like you could do that for for your own for your own benefit and learning alright we're almost well we could go forever right because there is no largest number I could keep going you know keep 2 times 9 times 10 times 100 Q times 1,000 times a million but I'm going to stop at 12 because that tends to be what people need to memorize but if you really want to be a math a mathlete you might want to go up to 20 let's go to 2 times 9 well it's going to be 2 more than 2 times 8 it's going to be 18 or that's 9 plus 9 also 18 what's 2 times 10 and 10 times tables are interesting and we're going to see a pattern there in a second when we look at when we do try to complete an entire times tables so 2 times 10 to more than 2 times 9 it's 20 all right or we could also say that's 10 plus 10 10 plus itself two times now what's interesting about this this looks just like a 2 with a zero in it and you're going to see that anything times 10 you just put a zero on the right and you can think about why that is this is you can view this as two tens is 20 that's what 20 is we're almost done let's do 2 times 11 2 times 11 is going to be 2 more than this right here it's going to be 22 another interesting pattern I have the number repeated twice a2 and a2 interesting something to to watch out for and as we as we look at other multiplication tables and then finally it's not finally we could keep going two times that's too dark of a color two times twelve two times twelve is going to be two more than two times eleven is twenty four could have also written that is 12 plus twelve or we're going to said 2 plus 2 plus 2 plus 2 plus 2 12 times it all gets you to 24 so that's the two times table and I think you see the pattern every time you multiply it by one higher number you just add 2 to that number so now that we see that pattern let's see if we can complete a multiplication table so what I'm going to do I'm going to write all of the numbers let's see 1 I hope I have space for this 1 2 3 4 5 6 7 8 9 actually I'll just do it till not I'll just keep going 9 actual I won't have space to do that because I want you to see the entire table so I'm just going to line here but I encourage you after this video to complete it on your own maybe if we have time I'll complete it here as well so this is the first numbers that I'm going to multiply and I'm going to multiply it times 1 2 3 4 5 6 7 8 and 9 what I'm going to do is I'm going to so first of all actually I should have written this one under it what what's 1 times 1 so this is the way I'm going to view that whatever is 1 times 1 I'm going to write here well that's 1 what's 1 times 2 that's 2 what's 1 times 3 that's 3 1 times anything is that number so I could just write 4 5 6 7 8 9 right 1 times 9 is 9 fair enough now let's do the 2 times tables I'll do that in the blue actually let me do one in that color and now in maybe a darker blue alter the two times table what's 2 times 1 well that's 2 the same thing as 1 times 2 notice these two numbers are the same thing what's 2 times 2 that's 4 2 times 3 is 6 we just did this every every time you increment or you go you multiply by hi where you just add by two two times four is eight same thing as 4 times 2 2 times 5 is 10 2 times 6 is 12 I'm just adding 2 every time right up here added one from every step here I'm adding 2 2 times 7 14 2 times 8 16 2 times 9 18 all right let's do our 3 times tables I'll do it in yellow yellow 3 times 1 is 3 notice 3 times 1 is 3 1 times 3 is 3 these are the same values 3 times 2 is the same thing as 2 times 3 right 3 times 3 times 2 should be the same thing as 2 times 3 so it's 6 and that makes sense 3 plus 3 is 6 or 2 plus 2 plus 2 is 6 so every time here we're going to increase by 3 you see the pattern 3 times 3 is 9 3 plus 3 plus 3 so we went from 3 to 6 to 9 so 3 times 4 is going to be 12 I'm just adding 3 every time 12 plus 3 is 15 15 plus 3 is 18 18 plus 3 is 21 21 plus 3 is 24 24 plus 3 is 27 so 3 times 9 is 27 3 times 8 is 24 so if you were to say 8 plus 8 plus 8 it would be 24 let's see if I can so now I'm going to speed it up a little bit now that we see the pattern and you should do this on your own and you really should memorize everything we're doing you should actually go all the way up to 12 in both directions so let's see 4 times 1 is 4 now I'm just going to go up by increments of 4 so 4 plus 4 is 8 8 plus 4 is 12 12 plus 4 is 16 16 plus 4 is 20 20 plus 4 is 24 right 4 times 6 is 24 4 times 7 28 I'm just going up by 4 32 and 36 36 all right 5 times 1 5 times 1 is going to be let me do this five times one is going to be five actually we know that anything that what I want to keep changing colors so I'll just do it in rolls like this 5 times 1 is 5 5 times 2 is 10 5 times 3 is 15 I'm just going to increase by 5 5 times tables are very fun as well because every number is going to add if we multiply 5 times well we'll learn about even and odd in the future but every other number every other number in its times tables is going to end with a 5 and then every other one is going to end with the 0 because if you add 5 to 15 you get 20 you get 25 30 35 40 45 enough 6 times tables let me do it in green 6 times 1 is 6 that's easy you had 6 to that you get 12 you add 6 to that you get 18 you had 6 to that you get 24 you had 6 to that you get 30 then you go six more 36 42 48 48 plus 6 is 54 so 6 times 9 is 54 all right we're almost there 7 times 1 that's 7 7 times 1 is 7 7 times 2 is 14 7 times 3 21 7 times 4 28 7 times 5 what's what's 28 plus 7 let's see if you add 2 you to 30 then you have 5 us 7 times 6 42 7 times 7 49 7 times 8 7 times is going to be 7 plus this what's 56 I always used to get confused between 7 times 8 being 56 and 6 times 9 being 54 so now that I pointed out to you that I always got confused between those two it's your job not to be confused by those 2 7 times 8 you could say has the six in it 6 times 9 doesn't have the 6 in it that's the way I think of it anyway 7 times 9 we're going to add another 7 here it's going to be 63 to do it in that same color 63 all right we're at our 8 times tables 8 times 1 is 8 8 times 2 16 24 right 8 times 3 is 24 and if we go to 3 times 8 we should also see the 24 yep it's there all right these values are the same so we're actually doing things twice we're doing it when and you do 8 times 3 or doing any when we did 3 times 8 let's see 8 times 4 I'm going to add 8 to it 30 to 40 add another 848 notice 8 times 6 48 6 times 8 48 all right 8 times 7 well we already pointed that one out that was 56 8 times 8 64 8 times 9 and 8 to this is 72 now we're at the 9 times tables I'm running out of colors well maybe I'll reuse a color or two I'll use the blue again 9 times 1 is 9 9 times 2 18 9 times 3 we actually know all of these if we could look it up in the rest of the table because 9 times 3 is the same thing as 3 times 9 is 27 add 9 to that 27 plus 9 is 36 36 Plus 9 is 45 notice every time you add 9 you go almost up by 10 but 1 less than that so up by 10 would be 46 and then 1 less than that is 45 but anyway we'll talk about look notice the ones did well I'll talk more about in the future but we go from a 9 8 7 6 5 on this digit on the second digit and on the on the set the this digit here you go 1 2 3 4 so it's an interesting pattern another interesting pattern is the digits will add up to 9 3 plus 6 is 9 2 plus 7 is 9 we'll talk more about that in the future maybe prove that to you 9 times 654 that was this one as well 9 times 7 63 9 times 8 72 9 times 1 is 81 if you can see that 81 there you go now I could keep going actually I should keep going let me well I realized this video is already pretty long in the next video I want you to memorize this right now because this is going to get you pretty far in the next video I'm going to do the times tables past 9 see you soon