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.

Choose “Save as PDF” to keep a copy. Use your browser’s paper setting for A4 or Letter.

Worksheet StudioPractice pack · Ages 7-9

Take your time. Show your thinking.

1. How many more do you need to add to 8 to make 20?
8 · 20 · Complements to 10, 20 & 100
2. How many more do you need to add to 21 to make 50?
21 · 50 · Complements to 10, 20 & 100
3. How many more do you need to add to 26 to make 50?
26 · 50 · Complements to 10, 20 & 100
4. How many more do you need to add to 1 to make 20?
1 · 20 · Complements to 10, 20 & 100
5. How many more do you need to add to 27 to make 50?
27 · 50 · Complements to 10, 20 & 100
6. How many more do you need to add to 12 to make 20?
12 · 20 · Complements to 10, 20 & 100
7. How many more do you need to add to 4 to make 50?
4 · 50 · Complements to 10, 20 & 100
8. How many more do you need to add to 57 to make 100?
57 · 100 · Complements to 10, 20 & 100
9. How many more do you need to add to 15 to make 30?
15 · 30 · Complements to 10, 20 & 100
10. How many more do you need to add to 16 to make 20?
16 · 20 · Complements to 10, 20 & 100
11. How many more do you need to add to 77 to make 100?
77 · 100 · Complements to 10, 20 & 100
12. How many more do you need to add to 37 to make 50?
37 · 50 · Complements to 10, 20 & 100

12 questions · Seed 104732 · 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 8 to make 20?
12
Subtract 8 from 20: 20 − 8 = 12.
2. How many more do you need to add to 21 to make 50?
29
Subtract 21 from 50: 50 − 21 = 29.
3. How many more do you need to add to 26 to make 50?
24
Subtract 26 from 50: 50 − 26 = 24.
4. How many more do you need to add to 1 to make 20?
19
Subtract 1 from 20: 20 − 1 = 19.
5. How many more do you need to add to 27 to make 50?
23
Subtract 27 from 50: 50 − 27 = 23.
6. How many more do you need to add to 12 to make 20?
8
Subtract 12 from 20: 20 − 12 = 8.
7. How many more do you need to add to 4 to make 50?
46
Subtract 4 from 50: 50 − 4 = 46.
8. How many more do you need to add to 57 to make 100?
43
Subtract 57 from 100: 100 − 57 = 43.
9. How many more do you need to add to 15 to make 30?
15
Subtract 15 from 30: 30 − 15 = 15.
10. How many more do you need to add to 16 to make 20?
4
Subtract 16 from 20: 20 − 16 = 4.
11. How many more do you need to add to 77 to make 100?
23
Subtract 77 from 100: 100 − 77 = 23.
12. How many more do you need to add to 37 to make 50?
13
Subtract 37 from 50: 50 − 37 = 13.

12 questions · Seed 104732 · 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 8 to make 20?
8 · 20 · Complements to 10, 20 & 100
2. How many more do you need to add to 21 to make 50?
21 · 50 · Complements to 10, 20 & 100
3. How many more do you need to add to 26 to make 50?
26 · 50 · Complements to 10, 20 & 100
4. How many more do you need to add to 1 to make 20?
1 · 20 · Complements to 10, 20 & 100
5. How many more do you need to add to 27 to make 50?
27 · 50 · Complements to 10, 20 & 100
6. How many more do you need to add to 12 to make 20?
12 · 20 · Complements to 10, 20 & 100
7. How many more do you need to add to 4 to make 50?
4 · 50 · Complements to 10, 20 & 100
8. How many more do you need to add to 57 to make 100?
57 · 100 · Complements to 10, 20 & 100
9. How many more do you need to add to 15 to make 30?
15 · 30 · Complements to 10, 20 & 100
10. How many more do you need to add to 16 to make 20?
16 · 20 · Complements to 10, 20 & 100
11. How many more do you need to add to 77 to make 100?
77 · 100 · Complements to 10, 20 & 100
12. How many more do you need to add to 37 to make 50?
37 · 50 · Complements to 10, 20 & 100

12 questions · Seed 104732 · 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 8 to make 20?
12
Subtract 8 from 20: 20 − 8 = 12.
2. How many more do you need to add to 21 to make 50?
29
Subtract 21 from 50: 50 − 21 = 29.
3. How many more do you need to add to 26 to make 50?
24
Subtract 26 from 50: 50 − 26 = 24.
4. How many more do you need to add to 1 to make 20?
19
Subtract 1 from 20: 20 − 1 = 19.
5. How many more do you need to add to 27 to make 50?
23
Subtract 27 from 50: 50 − 27 = 23.
6. How many more do you need to add to 12 to make 20?
8
Subtract 12 from 20: 20 − 12 = 8.
7. How many more do you need to add to 4 to make 50?
46
Subtract 4 from 50: 50 − 4 = 46.
8. How many more do you need to add to 57 to make 100?
43
Subtract 57 from 100: 100 − 57 = 43.
9. How many more do you need to add to 15 to make 30?
15
Subtract 15 from 30: 30 − 15 = 15.
10. How many more do you need to add to 16 to make 20?
4
Subtract 16 from 20: 20 − 16 = 4.
11. How many more do you need to add to 77 to make 100?
23
Subtract 77 from 100: 100 − 77 = 23.
12. How many more do you need to add to 37 to make 50?
13
Subtract 37 from 50: 50 − 37 = 13.

12 questions · Seed 104732 · Age guidance, not curriculum certification