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# Adding and subtracting on number line

CCSS.Math:

## Video transcript

which number line shows 361 plus 544 so let's see and all of them were starting at 361 so now let's add 544 so this one starts by adding 400 and then 50 and then for its adding 454 not 544 now this one adds 500 then 40 and then 4 so this is adding 544 to 361 and we see that it is 905 so this makes sense you had 500 you get 861 you add 40 you get to 901 and then you add the for you to 905 so definitely go with that choice this one over here instead of adding 500 you add 50 which doesn't make sense because we're clearly adding five hundreds four tens or 40 and then four ones let's do some more examples which expression can be solved with the following number line so let's see we're starting at 718 and then we're adding 200 and then we're adding 40 to get to 958 so this is really 718 plus 240 which is this choice right over there this is kind of strangely fun which number line shows 585 - 368 let's see these these second two number lines both start at 585 where we're starting our computation at 585 this one's starting at 558 so it's swapped the numbers so this one doesn't make sense but let's look at this these two choices so we want to subtract three hundreds 610 s and eight ones so in both of these we subtract three hundreds and then we want to subtract six tens six tens and then eight once that's this one over here this one swaps the instead of having six tens and eight ones it has eight tens and six ones so it's swapped this is subtracting 386 which isn't the original problem so it definitely like this third choice let's do one more example which expression has been solved with the following number line so we're starting at 935 and then we're going to subtract 400 and then we're going to subtract 20 so this is 935 - 420 935 - 420 and that choice right over there