Subtraction Within 20 Across 10: Worksheet 1
The trickiest step of first-grade subtraction, thirty times in a row: subtraction within 20 across 10, for children aged 6-8 who know their facts within 10.
2 A4 pages · for home and classroom use
Labugen
Subtraction up to 20 with regrouping
set no. 7301
- 1.15 - 7 =
- 2.20 - 1 =
- 3.20 - 14 =
- 4.11 - 5 =
- 5.20 - 11 =
- 6.13 - 7 =
- 7.20 - 12 =
- 8.11 - 3 =
- 9.11 - 4 =
- 10.10 - 7 =
- 11.11 - 6 =
- 12.10 - 4 =
- 13.14 - 9 =
- 14.10 - 6 =
- 15.12 - 9 =
- 16.10 - 8 =
- 17.13 - 5 =
- 18.10 - 2 =
- 19.12 - 3 =
- 20.11 - 7 =
- 21.14 - 8 =
- 22.20 - 4 =
- 23.20 - 17 =
- 24.17 - 8 =
- 25.13 - 6 =
- 26.13 - 9 =
- 27.15 - 6 =
- 28.15 - 9 =
- 29.14 - 5 =
- 30.10 - 9 =
How to use this worksheet
- Start with problem 1, 15 − 7. Say: "First take 5 to get down to 10, then 2 more: 8."
- Next, find the six problems that start at 10, such as 10 − 7 and 10 − 4; they use bonds to 10 directly.
- Then do the six that start at 20, such as 20 − 14 and 20 − 17: take away the ten first, then the ones.
- Finish the teen problems and check everything with the answer page.
What this worksheet teaches
In every problem the ones digit of the first number is smaller than the number taken away, so the answer drops below the ten you started in. Eighteen problems start from a teen number (15 − 7, 11 − 5, 14 − 9), six start from 10 and six from 20 (20 − 1, 20 − 11, 20 − 4). All answers fall between 1 and 19. The page builds the strategies needed later for borrowing in columns.
Subtract through ten
Break the number you take away so you land on 10 first: 13 − 5 = 13 − 3 − 2 = 8, and 14 − 9 = 14 − 4 − 5 = 5. The other route is to think addition: for 15 − 7, ask "7 and what make 15?" Since 7 + 8 = 15, the answer is 8. Children often settle on the route they like best; both are correct.