Count Up to Subtract Within 20
Count up from the smaller number to the larger one. The distance is the difference.
13 − 9 is not a new fact if you can add. It asks how far it is from 9 up to 13. You are finding the missing addend in 9 + ? = 13. Stop on 10 so each jump is small.
Start at 9, the number being taken away. The first jump reaches 10, and that jump is 1. The second jump goes from 10 to 13, and that jump is 3. Add the jumps: 1 + 3 = 4. So 13 − 9 = 4. Check with addition: 9 + 4 = 13.
- Start at the number you are taking away. Do not count it as a step.
- Jump to the next ten and remember how far that was.
- Jump from that ten to the larger number.
- Add the two jumps. That sum is the difference.
12 − 8: from 8 to 10 is 2, from 10 to 12 is 2, and 2 + 2 = 4. 14 − 9: from 9 to 10 is 1, from 10 to 14 is 4, and 1 + 4 = 5. 11 − 8: from 8 to 10 is 2, from 10 to 11 is 1, and 2 + 1 = 3.
Watch out
- Counting the starting number as one of the jumps.
- Adding the two original numbers instead of the distance between them.
- Forgetting the little jump that lands on 10.
What is 12 − 8?
8 to 10 is 2, and 10 to 12 is 2. 2 + 2 = 4. Check: 8 + 4 = 12.
What is 14 − 9?
9 to 10 is 1, and 10 to 14 is 4. 1 + 4 = 5. Check: 9 + 5 = 14.
Math practice for Count Up to Subtract
Subtract within 20
Practice this