Video: Adding Three-Digit Numbers to Solve Word Problems

If there are 342 boys and 200 girls in a school, how many students are there?

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Video Transcript

If there are 342 boys and 200 girls in a school, how many students are there?

In this question, we’re given two parts of a whole amount. If there are 342 boys and 200 girls, to find the number of students there are, we know we need to add these two amounts together. In other words, what is 342 plus 200? Now there’s something interesting about the number that we’re adding on to 342 here. Can you see what it is? 200 is a multiple of 100. It’s what we get when we count on in hundreds twice: 100, 200. And so to add 200 to 342, all we have to do is to think about the hundreds digits.

And you know, before we even start, we can make a prediction here. We can say that the number of tens and ones are going to stay the same. 342 has four 10s and two ones. And that’s why we know that our answer is going to have four 10s and two ones, too. We just need to think about combining our two 100s together. That’s 300 and another 200. Now we know three plus two equals five. So 300 plus another 200 is going to make 500. We found the answer quickly here, simply by adding on the hundreds that we needed to. If there are 342 boys and 200 girls in a school, the number of students that there are altogether is 542.

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