Video: Adding Four Numbers up to 99

What is the sum of 61, 90, 87, and 49?

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Video Transcript

What is the sum of 61, 90, 87, and 49?

Let’s start by setting up an addition problem. 61 plus 90 plus 87 plus 49. We treat this the same way we will treat adding two numbers together. We first add up everything in the ones place. One plus seven plus nine equals 17. We write a seven in the ones place. And we carry a one to the tens place.

After that, we add up all the digits in the tens place. One plus six plus nine plus eight plus four. One way we can do that is by grouping things that add up to 10. Here, I might notice that one plus nine equals 10. And six plus four equals 10. 10 plus 10 equals 20. But we can’t forget our eight, still in the tens place. So we add eight plus 20. And that equals 28.

The sum of these four values equals 287.

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