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# Multiplying by multiples of 10

CCSS.Math:

## Video transcript

let's see if we can figure out three times 60 well there's a couple of ways you could think about it you could literally view this as 63 times so you could view this as 60 plus 60 plus 60 and you might be able to compute this in your head 60 plus 60 is 120 plus another 60 is 180 and you'd be done but another way to think about this is that three times 60 is the same thing as three times instead of thinking of it as 60 you could think of 60 as 6 times 10 3 times 6 times 10 and when you're multiplying three numbers like this it doesn't matter what order you multiply them in so we could multiply the 3 times 6 first and get 18 and then multiply that times 10 and 18 times 10 is just going to be 180 it's going to be 18 with another zero so this is going to be 100 180 now you the more practice you get here you'll realize like I could have just said 3 times 6 is 18 but I have to worry about this zero right over here so I'm going to put one more zero at the end it's going to be 180 same answer that we got right over there let's do another one of these so let's say we want to multiply so we want to multiply 50 times 7 and I encourage you to think pause the video and think about it yourself and then unpause it and see what I do so 50 well there's a couple of ways you could think about it one you could literally try to add 57 times adding 750 times would be take forever but you could literally save 50 plus 50 plus 50 plus 50 let's see that's 4 plus 50 plus 50 let's see that is 6 I'll do one more right over here 50 right over here so this is 57 times if you add together 50 plus 50 is 100 150 200 250 300 350 so you could do it that way but you could imagine that there is an easier way to do it you just need to realize that 50 is the same thing as 10 times 5 so we could write this as 10 times 5 and then we're multiplying that times seven once again the order that we multiply does not matter so you can multiply the 5 times the 7 first we know that that is 35 and we're going to multiply that we're going to multiply that times 10 10 times 35 well we're just going to stick a zero at the end of the 35 is going to be equal to 300 350 now I want to do that zero in that same color is going to be 350 now you might realize hey look I could have just looked at this 5 right over here multiply the 5 times the 7 and have gotten the 35 and then not forgetting that it's actually not a 5 it's a 50 so I have to multiply by 10 again or I have to throw that zero at the end of it to get that zero right over here so 50 times seven is 350