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 14 to make 20?
14 · 20 · Complements to 10, 20 & 100
2. How many more do you need to add to 38 to make 100?
38 · 100 · Complements to 10, 20 & 100
3. How many more do you need to add to 13 to make 20?
13 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 84 to make 100?
84 · 100 · Complements to 10, 20 & 100
5. How many more do you need to add to 21 to make 30?
21 · 30 · Complements to 10, 20 & 100
6. How many more do you need to add to 22 to make 100?
22 · 100 · Complements to 10, 20 & 100
7. How many more do you need to add to 28 to make 30?
28 · 30 · Complements to 10, 20 & 100
8. How many more do you need to add to 13 to make 50?
13 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 6 to make 20?
6 · 20 · 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 20 to make 50?
20 · 50 · Complements to 10, 20 & 100
12. How many more do you need to add to 5 to make 50?
5 · 50 · Complements to 10, 20 & 100

12 questions · Seed 104778 · 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 14 to make 20?
6
Subtract 14 from 20: 20 − 14 = 6.
2. How many more do you need to add to 38 to make 100?
62
Subtract 38 from 100: 100 − 38 = 62.
3. How many more do you need to add to 13 to make 20?
7
Subtract 13 from 20: 20 − 13 = 7.
4. How many more do you need to add to 84 to make 100?
16
Subtract 84 from 100: 100 − 84 = 16.
5. How many more do you need to add to 21 to make 30?
9
Subtract 21 from 30: 30 − 21 = 9.
6. How many more do you need to add to 22 to make 100?
78
Subtract 22 from 100: 100 − 22 = 78.
7. How many more do you need to add to 28 to make 30?
2
Subtract 28 from 30: 30 − 28 = 2.
8. How many more do you need to add to 13 to make 50?
37
Subtract 13 from 50: 50 − 13 = 37.
9. How many more do you need to add to 6 to make 20?
14
Subtract 6 from 20: 20 − 6 = 14.
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 20 to make 50?
30
Subtract 20 from 50: 50 − 20 = 30.
12. How many more do you need to add to 5 to make 50?
45
Subtract 5 from 50: 50 − 5 = 45.

12 questions · Seed 104778 · 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 14 to make 20?
14 · 20 · Complements to 10, 20 & 100
2. How many more do you need to add to 38 to make 100?
38 · 100 · Complements to 10, 20 & 100
3. How many more do you need to add to 13 to make 20?
13 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 84 to make 100?
84 · 100 · Complements to 10, 20 & 100
5. How many more do you need to add to 21 to make 30?
21 · 30 · Complements to 10, 20 & 100
6. How many more do you need to add to 22 to make 100?
22 · 100 · Complements to 10, 20 & 100
7. How many more do you need to add to 28 to make 30?
28 · 30 · Complements to 10, 20 & 100
8. How many more do you need to add to 13 to make 50?
13 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 6 to make 20?
6 · 20 · 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 20 to make 50?
20 · 50 · Complements to 10, 20 & 100
12. How many more do you need to add to 5 to make 50?
5 · 50 · Complements to 10, 20 & 100

12 questions · Seed 104778 · 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 14 to make 20?
6
Subtract 14 from 20: 20 − 14 = 6.
2. How many more do you need to add to 38 to make 100?
62
Subtract 38 from 100: 100 − 38 = 62.
3. How many more do you need to add to 13 to make 20?
7
Subtract 13 from 20: 20 − 13 = 7.
4. How many more do you need to add to 84 to make 100?
16
Subtract 84 from 100: 100 − 84 = 16.
5. How many more do you need to add to 21 to make 30?
9
Subtract 21 from 30: 30 − 21 = 9.
6. How many more do you need to add to 22 to make 100?
78
Subtract 22 from 100: 100 − 22 = 78.
7. How many more do you need to add to 28 to make 30?
2
Subtract 28 from 30: 30 − 28 = 2.
8. How many more do you need to add to 13 to make 50?
37
Subtract 13 from 50: 50 − 13 = 37.
9. How many more do you need to add to 6 to make 20?
14
Subtract 6 from 20: 20 − 6 = 14.
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 20 to make 50?
30
Subtract 20 from 50: 50 − 20 = 30.
12. How many more do you need to add to 5 to make 50?
45
Subtract 5 from 50: 50 − 5 = 45.

12 questions · Seed 104778 · Age guidance, not curriculum certification