Subtraction Within 20 — Answer Key
Part A: Fill in the Missing Number
Write the missing number to complete each subtraction sentence.
1. 11 - 4 = 7
Since ___ - 4 = 7, the missing number is 4 + 7 = 11.
2. 16 - 7 = 9
Since 16 - ___ = 9, the missing number is 16 - 9 = 7.
3. Start at 15. Count back 6. You land on 9.
Starting at 15 and counting back 6 lands on 9.
4. 20 - 8 = 12
Since 20 - ___ = 12, the missing number is 20 - 12 = 8.
5. 17 - 8 = 9
Since ___ - 8 = 9, the missing number is 8 + 9 = 17.
6. Start at 18. Count back 7. You land on 11.
Starting at 18 and counting back 7 lands on 11.
7. If 8 + 6 = 14, then 14 - 6 = 8.
This uses the fact family relationship. Since 8 + 6 = 14, then 14 - 6 = 8.
8. 13 - 8 = 5
Since 13 - ___ = 5, the missing number is 13 - 5 = 8.
9. If 9 + 5 = 14, then 14 - 5 = 9.
This uses the fact family relationship. Since 9 + 5 = 14, then 14 - 5 = 9.
Part B: Match the Problem to Its Answer
Draw a line from each subtraction problem to its correct answer.
1. Match each subtraction problem to its answer.
15 - 7
→ 8
9
18 - 9
→ 9
7
14 - 8
→ 6
6
20 - 13
→ 7
8
Match each subtraction to its difference: 15 - 7 = 8, 18 - 9 = 9, 14 - 8 = 6, 20 - 13 = 7.