Question Video: Adding Multiples of 10 to a Two-Digit Number Mathematics • 1st Grade

Complete the number sentence: 88 + 10 = _.

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Video Transcript

Complete the number sentence: 88 plus 10 equals what.

In this question, we’re given a two-digit number, 88, and we need to find 10 more than it. Now, the number 88 is made up of some tens already, some tens and some ones. And to help us understand what happens to 88 when we add 10 to it, let’s break it apart into its tens and ones. 88 is one of those numbers that has the same number of tens as it does ones. It’s made up of eight 10s and eight ones. And the number that we’re adding, 10, is just the same as one 10, isn’t it? There aren’t any ones. So if we look at our place value blocks, we can see we already have eight 10s and we just need to add one more 10. Can you see how many tens we’re going to get? Our number of tens has increased by one. Instead of eight 10s, we now have nine 10s.

But the ones in our number haven’t changed at all. We haven’t had anything to add there. And because we’ve added 10, our part–whole model doesn’t quite make sense now, so let’s rub out 88 on the top. And we’ll replace it with our answer, which has nine 10s, eight ones. 98. To help us add 10, we broke apart 88 into eight 10s and eight ones. And by adding one more 10, we ended with a number that has nine 10s and eight ones. 88 plus 10 equals 98.

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