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Current time:0:00Total duration:6:13

CCSS.Math:

let's solve 240 divided by 3 to solve this we could take this large three-digit number and divide it by one digit number or we could take what we know about tens about zeros and tens and try to break this up into numbers that might be easier for us to work with so 240 because the zero on the end I know is the same as 20 for ten or twenty four times 1024 times ten anytime we multiply by ten we'll have the original number 24 in this case with a zero on the end 240 so 240 is the same as 24 10 or 10 times 24 so we can come back over here and write this number 240 as 24 times 10 and then still have the divided by 3 at the end so what we changed was to change 240 or 24 tends to be 24 times 10 what we did not change is the solution these expressions are still equal to equal the same number so we can solve either one to get the same solution and down here we have a little bit simpler of numbers to work with so I'll work with this one down here the next thing I'm going to do is look at this multiplication problem 24 times 10 and I know that in multiplication I can multiply in any order for example if I have something like 2 times 3 which is 6 that's the same as 3 times 2 which is also 6 two threes or three twos is 6 we can change the order without changing the answer so over here let's do that 10 times 24 divided by 3 so we've changed the expression we've changed what's written here but we have not changed what it equals we have not changed the solution and now I can see a division problem that for me is far simpler than this big three-digit division problem up here 24 divided into groups of 3 is 8 with 8 and then we'll bring down our times 10 bringing down this 10 and the time side and then we can use the pattern we already know that we talked about up here when we multiply by 10 we take our whole number in this case 8 and we add a zero to the end or 80 so our solution we came up with 80 which means our solution to the original expression is also 80 240 divided by 3 is 8 tens or 80 one other way we could have thought about this is 240 as we've already said is 24 tens if we divide 24 tens by 3 we end up with eight tens and eight tens is equal to 80 if we have eight tens that equals 80 so this is one other way that we could have thought about it both ways using the zero or our knowledge of tens to break this division problem down so we didn't have to deal with a large three-digit number book a deal with simpler smaller numbers let's try another one this time let's do thousands let's make this one trickier what about something like 4200 or four thousand two hundred divided by and let's see how about seven divided by seven so here again we can break this number down 4200 this number 4200 or four thousand two hundred can be written as forty-two times 100 because our pattern tells us when we have a number like a whole number like 42 and we multiply by a hundred we keep our whole number of 42 and we add two zeros now so 42 times 100 and then we still need to have our divided by seven at the end reverse these numbers so that 42 and 7 can be next to each other 42 divided by 7 because that's a division problem a division fact we might already know 42 divided in groups of 7 is 6 and bring down the hundred and the time sign a hundred times 6 is 600 so our solution going back up here to 4d 200 divided by 7 is 600 or we could have thought about it again still thinking about place value but using words here instead of digits 4200 is 4,200 s42 I can write that out 42 hundreds and if you divide 42 hundreds into groups of seven or into seven groups each group will have six hundreds or 600 in it so either way 4,200 4,200 divided by seven is 600 so here again we were able to solve a tricky problem when they had a four digit number without using any long division but instead using what we know about place value or hundreds and zeroes