MathsAges 7-9

Complements to 10, 20 & 100

Find how many more are needed to complete a benchmark number such as 10, 20, 50 or 100. Review suitability for your learners before teaching.

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Worksheet StudioPractice pack · Ages 7-9

Take your time. Show your thinking.

1. How many more do you need to add to 11 to make 20?
11 · 20 · Complements to 10, 20 & 100
2. How many more do you need to add to 4 to make 20?
4 · 20 · Complements to 10, 20 & 100
3. How many more do you need to add to 12 to make 20?
12 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 40 to make 50?
40 · 50 · Complements to 10, 20 & 100
5. How many more do you need to add to 84 to make 100?
84 · 100 · Complements to 10, 20 & 100
6. How many more do you need to add to 71 to make 100?
71 · 100 · Complements to 10, 20 & 100
7. How many more do you need to add to 82 to make 100?
82 · 100 · Complements to 10, 20 & 100
8. How many more do you need to add to 38 to make 50?
38 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 56 to make 100?
56 · 100 · Complements to 10, 20 & 100
10. How many more do you need to add to 17 to make 50?
17 · 50 · Complements to 10, 20 & 100
11. How many more do you need to add to 1 to make 20?
1 · 20 · Complements to 10, 20 & 100
12. How many more do you need to add to 8 to make 20?
8 · 20 · Complements to 10, 20 & 100

12 questions · Seed 43 · Age guidance, not curriculum certification

View the answer key

Worksheet StudioAnswer key · Ages 7-9

Answers and reasoning. Review before teaching.

1. How many more do you need to add to 11 to make 20?
9
Subtract 11 from 20: 20 − 11 = 9.
2. How many more do you need to add to 4 to make 20?
16
Subtract 4 from 20: 20 − 4 = 16.
3. How many more do you need to add to 12 to make 20?
8
Subtract 12 from 20: 20 − 12 = 8.
4. How many more do you need to add to 40 to make 50?
10
Subtract 40 from 50: 50 − 40 = 10.
5. How many more do you need to add to 84 to make 100?
16
Subtract 84 from 100: 100 − 84 = 16.
6. How many more do you need to add to 71 to make 100?
29
Subtract 71 from 100: 100 − 71 = 29.
7. How many more do you need to add to 82 to make 100?
18
Subtract 82 from 100: 100 − 82 = 18.
8. How many more do you need to add to 38 to make 50?
12
Subtract 38 from 50: 50 − 38 = 12.
9. How many more do you need to add to 56 to make 100?
44
Subtract 56 from 100: 100 − 56 = 44.
10. How many more do you need to add to 17 to make 50?
33
Subtract 17 from 50: 50 − 17 = 33.
11. How many more do you need to add to 1 to make 20?
19
Subtract 1 from 20: 20 − 1 = 19.
12. How many more do you need to add to 8 to make 20?
12
Subtract 8 from 20: 20 − 8 = 12.

12 questions · Seed 43 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 7-9

Take your time. Show your thinking.

1. How many more do you need to add to 11 to make 20?
11 · 20 · Complements to 10, 20 & 100
2. How many more do you need to add to 4 to make 20?
4 · 20 · Complements to 10, 20 & 100
3. How many more do you need to add to 12 to make 20?
12 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 40 to make 50?
40 · 50 · Complements to 10, 20 & 100
5. How many more do you need to add to 84 to make 100?
84 · 100 · Complements to 10, 20 & 100
6. How many more do you need to add to 71 to make 100?
71 · 100 · Complements to 10, 20 & 100
7. How many more do you need to add to 82 to make 100?
82 · 100 · Complements to 10, 20 & 100
8. How many more do you need to add to 38 to make 50?
38 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 56 to make 100?
56 · 100 · Complements to 10, 20 & 100
10. How many more do you need to add to 17 to make 50?
17 · 50 · Complements to 10, 20 & 100
11. How many more do you need to add to 1 to make 20?
1 · 20 · Complements to 10, 20 & 100
12. How many more do you need to add to 8 to make 20?
8 · 20 · Complements to 10, 20 & 100

12 questions · Seed 43 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 7-9

Answers and reasoning. Review before teaching.

1. How many more do you need to add to 11 to make 20?
9
Subtract 11 from 20: 20 − 11 = 9.
2. How many more do you need to add to 4 to make 20?
16
Subtract 4 from 20: 20 − 4 = 16.
3. How many more do you need to add to 12 to make 20?
8
Subtract 12 from 20: 20 − 12 = 8.
4. How many more do you need to add to 40 to make 50?
10
Subtract 40 from 50: 50 − 40 = 10.
5. How many more do you need to add to 84 to make 100?
16
Subtract 84 from 100: 100 − 84 = 16.
6. How many more do you need to add to 71 to make 100?
29
Subtract 71 from 100: 100 − 71 = 29.
7. How many more do you need to add to 82 to make 100?
18
Subtract 82 from 100: 100 − 82 = 18.
8. How many more do you need to add to 38 to make 50?
12
Subtract 38 from 50: 50 − 38 = 12.
9. How many more do you need to add to 56 to make 100?
44
Subtract 56 from 100: 100 − 56 = 44.
10. How many more do you need to add to 17 to make 50?
33
Subtract 17 from 50: 50 − 17 = 33.
11. How many more do you need to add to 1 to make 20?
19
Subtract 1 from 20: 20 − 1 = 19.
12. How many more do you need to add to 8 to make 20?
12
Subtract 8 from 20: 20 − 8 = 12.

12 questions · Seed 43 · Age guidance, not curriculum certification