Video: Adding a Single Digit to a Three-Digit Number by Breaking Parts

Find the total by first adding the ones. 352 + 7 = _

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Video Transcript

Find the total by first adding the ones. 352 plus seven equals what.

In this problem, we need to add a number of ones, which is seven, to a three-digit number, 352. And we’re told to find the total by first adding the ones. Now, if we look carefully at this calculation, we can see that the number 352 has been partitioned into 350 and two. Let’s have a think about why this might be, and how this could make it easier to add seven. Well, firstly, we know that 352 is made up of three hundreds, five tens, and two ones. And the number that we’re adding to 352, seven, can be represented by seven ones. Now, in the number seven, there aren’t any hundreds or tens that we need to add. It’s just a number of ones.

So to help us find the answer efficiently, we could partition the number 352 so that the ones are separate. We can see now this is exactly what’s happened in the part-whole model. On the right-hand side, we have the two ones that we’ve separated out. And on the left-hand side, we have the remaining part, 350. We can forget about this number to begin with because the very first thing we need to do is to add the ones together. We have two ones, and we need to add a further seven ones. What’s the total of two and seven? Or, we could think of it as seven and two. Two plus seven equals nine. Our answer is going to have nine ones in it.

But in order to find the answer to 352 plus seven, we’re going to need to combine our nine ones back with the other part, 350. In other words, we need to find the answer to 350 plus nine. 350 plus nine equals 359. We knew that the number that we were adding to 352 was a number of ones. And so, we decided to find the total by first adding those ones together. We partitioned the number 352 so that the ones were separate. And so, we had two ones which were ready to add to the seven ones on the rest of the number, 350. We then added the ones together to get the answer nine. And, finally, combined 350 back with our new total of nine ones to find the overall answer. 352 plus seven equals 359.

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