Missing Numbers

Find the unknown: 8 + ? = 10, ? − 2 = 5.

Warm-up, learn, try it together, practice, then a quick check. About 15 minutes.

What children learn in Level 20

Sometimes a number is missing, and a question mark stands in its place. 8 plus what equals 10?
Start at 8, and count on to 10: 9, 10. You counted 2. So 8 plus 2 equals 10.
This bar shows a whole and its two parts. The whole is 7. One part is 5. The other part is missing.
5 and 2 make 7, so the missing part is 2!
The missing number can be anywhere, even at the start: what number minus 2 equals 5? Put the parts back together: 5 plus 2 is 7. So 7 minus 2 equals 5.
Find the missing number by thinking about the parts and the whole.

Georgia's K-12 Mathematics Standards:

1.NR.2.6 — Determine the unknown whole number in an addition or subtraction equation relating to three whole numbers.