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 12 to make 50?
12 · 50 · Complements to 10, 20 & 100
2. How many more do you need to add to 38 to make 50?
38 · 50 · Complements to 10, 20 & 100
3. How many more do you need to add to 13 to make 50?
13 · 50 · Complements to 10, 20 & 100
4. How many more do you need to add to 3 to make 20?
3 · 20 · Complements to 10, 20 & 100
5. How many more do you need to add to 36 to make 50?
36 · 50 · Complements to 10, 20 & 100
6. How many more do you need to add to 69 to make 100?
69 · 100 · Complements to 10, 20 & 100
7. How many more do you need to add to 25 to make 50?
25 · 50 · Complements to 10, 20 & 100
8. How many more do you need to add to 37 to make 50?
37 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 40 to make 100?
40 · 100 · Complements to 10, 20 & 100
10. How many more do you need to add to 7 to make 20?
7 · 20 · Complements to 10, 20 & 100
11. How many more do you need to add to 4 to make 20?
4 · 20 · Complements to 10, 20 & 100
12. How many more do you need to add to 58 to make 100?
58 · 100 · Complements to 10, 20 & 100

12 questions · Seed 104781 · 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 12 to make 50?
38
Subtract 12 from 50: 50 − 12 = 38.
2. How many more do you need to add to 38 to make 50?
12
Subtract 38 from 50: 50 − 38 = 12.
3. How many more do you need to add to 13 to make 50?
37
Subtract 13 from 50: 50 − 13 = 37.
4. How many more do you need to add to 3 to make 20?
17
Subtract 3 from 20: 20 − 3 = 17.
5. How many more do you need to add to 36 to make 50?
14
Subtract 36 from 50: 50 − 36 = 14.
6. How many more do you need to add to 69 to make 100?
31
Subtract 69 from 100: 100 − 69 = 31.
7. How many more do you need to add to 25 to make 50?
25
Subtract 25 from 50: 50 − 25 = 25.
8. How many more do you need to add to 37 to make 50?
13
Subtract 37 from 50: 50 − 37 = 13.
9. How many more do you need to add to 40 to make 100?
60
Subtract 40 from 100: 100 − 40 = 60.
10. How many more do you need to add to 7 to make 20?
13
Subtract 7 from 20: 20 − 7 = 13.
11. How many more do you need to add to 4 to make 20?
16
Subtract 4 from 20: 20 − 4 = 16.
12. How many more do you need to add to 58 to make 100?
42
Subtract 58 from 100: 100 − 58 = 42.

12 questions · Seed 104781 · 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 12 to make 50?
12 · 50 · Complements to 10, 20 & 100
2. How many more do you need to add to 38 to make 50?
38 · 50 · Complements to 10, 20 & 100
3. How many more do you need to add to 13 to make 50?
13 · 50 · Complements to 10, 20 & 100
4. How many more do you need to add to 3 to make 20?
3 · 20 · Complements to 10, 20 & 100
5. How many more do you need to add to 36 to make 50?
36 · 50 · Complements to 10, 20 & 100
6. How many more do you need to add to 69 to make 100?
69 · 100 · Complements to 10, 20 & 100
7. How many more do you need to add to 25 to make 50?
25 · 50 · Complements to 10, 20 & 100
8. How many more do you need to add to 37 to make 50?
37 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 40 to make 100?
40 · 100 · Complements to 10, 20 & 100
10. How many more do you need to add to 7 to make 20?
7 · 20 · Complements to 10, 20 & 100
11. How many more do you need to add to 4 to make 20?
4 · 20 · Complements to 10, 20 & 100
12. How many more do you need to add to 58 to make 100?
58 · 100 · Complements to 10, 20 & 100

12 questions · Seed 104781 · 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 12 to make 50?
38
Subtract 12 from 50: 50 − 12 = 38.
2. How many more do you need to add to 38 to make 50?
12
Subtract 38 from 50: 50 − 38 = 12.
3. How many more do you need to add to 13 to make 50?
37
Subtract 13 from 50: 50 − 13 = 37.
4. How many more do you need to add to 3 to make 20?
17
Subtract 3 from 20: 20 − 3 = 17.
5. How many more do you need to add to 36 to make 50?
14
Subtract 36 from 50: 50 − 36 = 14.
6. How many more do you need to add to 69 to make 100?
31
Subtract 69 from 100: 100 − 69 = 31.
7. How many more do you need to add to 25 to make 50?
25
Subtract 25 from 50: 50 − 25 = 25.
8. How many more do you need to add to 37 to make 50?
13
Subtract 37 from 50: 50 − 37 = 13.
9. How many more do you need to add to 40 to make 100?
60
Subtract 40 from 100: 100 − 40 = 60.
10. How many more do you need to add to 7 to make 20?
13
Subtract 7 from 20: 20 − 7 = 13.
11. How many more do you need to add to 4 to make 20?
16
Subtract 4 from 20: 20 − 4 = 16.
12. How many more do you need to add to 58 to make 100?
42
Subtract 58 from 100: 100 − 58 = 42.

12 questions · Seed 104781 · Age guidance, not curriculum certification