Video: Adding Two Numbers up to 99

Complete the following: ＿ = 8 + 90.

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Video Transcript

Complete the following: the missing number is equal to eight plus 90. Is the missing number 98, 17, 89, 81, or 18?

The missing number is equal to eight plus 90. So we need to calculate this first. We could use our knowledge of place value and column addition to help us calculate the answer. So we’ve marked the tens place and the ones place.

We usually start by writing the greatest number first. 90 is greater than eight. And 90 has nine tens, which we can write in the tens place. 90 has no ones. So we can write this in the ones place. Next, we need to add eight. So we write eight in the ones place.

Let’s start by adding in the ones column: zero plus eight is eight. Let’s move across to the tens place or the tens column. We have nine tens, but nothing to add. So we can just write the answer nine in the tens place.

You can see that eight plus 90 or 90 plus eight equals 98. The missing number is 98. 98 is equal to eight plus 90. We calculated our answer using column addition and our knowledge of place value.