Question Video: Adding Three-Digit Numbers Using Partial Sum Mathematics

Find the total by first adding the hundreds. 265 + 300 = _


Video Transcript

Find the total by first adding the hundreds. 265 plus 300 equals what?

This question asks us to find the total. We know this means we need to add together the numbers to find the answer. We need to add together 265 and 300. Now, we know that the number 265 is made up of two hundreds, six tens, and five ones. And the number that we’re adding to 265 is 300, which is simply three hundreds. There are no tens and no ones. Because all we’re doing is adding a number of hundreds, the question tells us that we can find the total by first just adding the hundreds. So, let’s partition our number 265, so that we’re just looking at the hundreds.

We’ll move our two hundreds over here. There we go. On the left-hand side, instead of 265, we’re now left with just 65. And on the right-hand side, we’ve got 200. We’ve broken apart 265 into 65 and 200. And the reason we’ve done this is to make it easier to add the hundreds. Let’s do what the question says now then and first add the hundreds together. We have two hundreds, and we need to add another three hundreds. 100, 200, 300. We started with 200. We added 300. And, now we have 500. So, the two parts to our answer are 65, you can see this part of the number hasn’t changed at all, and also 500. This is the total of our two hundreds plus three hundreds.

To find the overall total, we need to combine both parts back together. What is 65 plus 500? The answer is 565. Because we were adding a number of hundreds to a three-digit number, we knew that we could partition the three-digit number and start by adding the hundreds together. 265 plus 300 equals 565.

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