Find the Missing Number
- Missing Number
A number sentence uses numbers and signs, like 4 + 3 = 7. A number sentence is also called an equation. A box like this shows a missing number. It is the number we need to find. The missing number is also called the unknown.
The box can be in any place. Some number sentences have three numbers. Some have four.
4 + 3 =
4 + = 7
− 3 = 4
6 + 4 = 3 +
Think: 8 plus what number makes 13? Count on from 8: 9, 10, 11, 12, 13. That is five more.
The missing number is 5.
8 + 5 = 13
The box is the number we start with. We take away 4 and have 9 left.
Put the 4 back to find the start. 9 + 4 = 13.
Check: 13 − 4 = 9. The missing number is 13.
13 − 4 = 9
This one has four numbers. First, add the side with no box. 6 + 4 = 10.
The equal sign means both sides make the same number. So 3 + must make 10. 3 + 7 = 10.
The missing number is 7.
6 + 4 = 3 + 7