Video: Simple Adding: Adding Multiples of Ten to Three-Digit Numbers

Find the sum by adding the tens first. 321 + 40 = _

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Video Transcript

Find the sum by adding the tens first. 321 plus 40 equals what?

In this question, we need to find the sum of two numbers. And, finding the sum means adding together. So, we need to add 321 and 40. 321 is made up of three 100s, two 10s, and one one. And, we need to add 40, which is the same as four 10s. The number 40 doesn’t have any hundreds or any ones in it. As we’ve said, it’s simply four 10s.

And so, we’re told that we can find the sum by adding the tens first. But to do this, we need to split up the number 321 to separate out the tens. That’s why we can see that the number 321 has been split into two parts. If we need to add the tens first, then we need to take the two 10s in 321 and put them in a part, all on their own. This is why 321 has been split into 301 and also 20. Separating out the tens like this makes it much easier to add our four 10s.

So, what do we get if we add four 10s to our two 10s? We get six 10s. We’ve added the tens first. 20 plus 40 equals 60. The number of tens in our answer will be six. But remember, we need to add our six 10s to our first part, which was 301. What is 301 plus our total of six 10s or 60? Let’s combine our tens total with the original number. Our answer has three 100s, six 10s and one one. We found the sum by adding the tens first. 321 plus 40 equals 361.

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