Subtracting Within 20 Without Regrouping: Worksheet 1
Half teen numbers, half small facts, and never a ten to break: subtracting within 20 without regrouping is the calm step for ages 6-7 before subtraction across ten.
2 A4 pages · for home and classroom use
Labugen
Subtraction up to 20 without regrouping
set no. 7302
- 1.18 - 13 =
- 2.12 - 10 =
- 3.5 - 2 =
- 4.8 - 6 =
- 5.14 - 12 =
- 6.19 - 9 =
- 7.19 - 3 =
- 8.3 - 1 =
- 9.5 - 3 =
- 10.18 - 10 =
- 11.17 - 6 =
- 12.19 - 18 =
- 13.17 - 11 =
- 14.4 - 1 =
- 15.17 - 12 =
- 16.6 - 1 =
- 17.17 - 7 =
- 18.18 - 5 =
- 19.2 - 1 =
- 20.8 - 5 =
- 21.19 - 1 =
- 22.18 - 12 =
- 23.7 - 5 =
- 24.6 - 3 =
- 25.17 - 4 =
- 26.5 - 1 =
- 27.4 - 3 =
- 28.8 - 4 =
- 29.9 - 4 =
- 30.7 - 4 =
How to use this worksheet
- Look at problem 25, 17 − 4. Cover the ten with a finger, work out 7 − 4 = 3, uncover the ten: 13.
- For problems where both numbers are teens, such as 18 − 13 or 17 − 11, subtract the ones and then the tens.
- Notice the problems that take away all the ones, 19 − 9 and 17 − 7: the answer is exactly 10.
- Check with the answer page.
What this worksheet teaches
In every problem the ones digit of the first number is at least as large as the ones digit taken away, so the ten never has to be broken. Fifteen problems start from a teen number (19 − 3, 18 − 5, 14 − 12) and fifteen stay within 10 (5 − 2, 8 − 6, 7 − 4). Answers range from 1 to 18. Subtracting from a teen number often changes only the ones, the idea behind column subtraction.
The ones do the work
Teen numbers are one ten and some ones. When the ones are enough, the ten can simply wait: 18 − 5 is 8 − 5 = 3 with the ten kept, so 13. When the number taken away has a ten too, take it away as well: 17 − 12 is 7 − 2 = 5 and 1 ten − 1 ten = 0, so 5. Taking away exactly ten, as in 18 − 10 and 12 − 10, leaves just the ones.