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# Breaking apart 3-digit addition problems

CCSS.Math:

## Video transcript

Mike isn't sure how to add 189 plus 608 help Mike by choosing an addition problem that is the same as 189 plus 608 now let's look at these choices so I should let's just start with let's just start with this first choice actually all of these choices start with having 100 they all have 100 so where do we see 100 here well in 189 we have a 1 in the hundreds place so this right over here that is 1 100 100 and then all of the choices actually have 600 600 600 so where are they getting that from well in 608 the six is in the hundreds so that six represents six hundreds six hundreds so that's where they got the 100 and the six hundreds from and then all of them have eight tens so they're actually all looking pretty similar up to that point they all have 810 810 810 s where do they get that from well in 189 this 8 is in the tens place so it represents eight tens eight tens and then what else do they have well this is where they all start to be a little bit different so let's go one by one so this next one has it then has nine ones nine ones where are they getting that from well in 189 the nine is in the ones place so it's reasonable to write nine ones and then finally they have eight ones eight ones where do they get that from well in 608 the eight is in the ones place so it's eight ones so this first choice is looking quite good now you might be saying okay we took into account all of these digits except for this is zero over here how come we didn't how come this is there's zero here in the tens place well that would just be zero tens zero tens which is just zero so it's not going to change the value of this so this first choice is indeed the same as the original as the original addition problem if we want to see where these other the other ones break down this one has eight tens written twice well we only have one so this we have an eight 10s here but this eight isn't is one so this should say ones over here and this choice we have the eight ones but this nine right over here this is once this isn't tens so this should be once and so that's why we wouldn't pick either of those let's do another one of these or at least a related type of problem which addition problem is the same as 525 plus 379 so let's just break it down so we have a five in the hundreds place so that would be 500 and then we have a 3 in the hundreds place so plus 300 then then we have a 2 in the tens place so that's two tens or 20 and then we have a seven in the tens place so that's plus 70 and then last but not least we have a 5 in the ones place so that's just going to be five and then we have a nine in the ones place so that's just going to be equal to nine so which of these choices is the same is what I just wrote over here so 500 plus 300 so this first choice has no 500 or 300 yet so we can rule that out 500 plus 300 plus 20 plus 70 Plus 5 plus 9 that's exactly what I wrote down this last choice breaks down they wrote 90 instead of 9 and then they wrote 5 and then they wrote seven instead of 70 that 7 is in the tens place it's not in the it's not in the ones place we ruled that one out as well