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 98 to make 100?
98 · 100 · Complements to 10, 20 & 100
2. How many more do you need to add to 3 to make 20?
3 · 20 · Complements to 10, 20 & 100
3. How many more do you need to add to 28 to make 50?
28 · 50 · Complements to 10, 20 & 100
4. How many more do you need to add to 27 to make 100?
27 · 100 · Complements to 10, 20 & 100
5. How many more do you need to add to 82 to make 100?
82 · 100 · Complements to 10, 20 & 100
6. How many more do you need to add to 18 to make 20?
18 · 20 · Complements to 10, 20 & 100
7. How many more do you need to add to 27 to make 50?
27 · 50 · Complements to 10, 20 & 100
8. How many more do you need to add to 33 to make 100?
33 · 100 · Complements to 10, 20 & 100
9. How many more do you need to add to 4 to make 30?
4 · 30 · Complements to 10, 20 & 100
10. How many more do you need to add to 22 to make 100?
22 · 100 · Complements to 10, 20 & 100
11. How many more do you need to add to 26 to make 50?
26 · 50 · Complements to 10, 20 & 100
12. How many more do you need to add to 21 to make 30?
21 · 30 · Complements to 10, 20 & 100

12 questions · Seed 104751 · 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 98 to make 100?
2
Subtract 98 from 100: 100 − 98 = 2.
2. How many more do you need to add to 3 to make 20?
17
Subtract 3 from 20: 20 − 3 = 17.
3. How many more do you need to add to 28 to make 50?
22
Subtract 28 from 50: 50 − 28 = 22.
4. How many more do you need to add to 27 to make 100?
73
Subtract 27 from 100: 100 − 27 = 73.
5. How many more do you need to add to 82 to make 100?
18
Subtract 82 from 100: 100 − 82 = 18.
6. How many more do you need to add to 18 to make 20?
2
Subtract 18 from 20: 20 − 18 = 2.
7. How many more do you need to add to 27 to make 50?
23
Subtract 27 from 50: 50 − 27 = 23.
8. How many more do you need to add to 33 to make 100?
67
Subtract 33 from 100: 100 − 33 = 67.
9. How many more do you need to add to 4 to make 30?
26
Subtract 4 from 30: 30 − 4 = 26.
10. How many more do you need to add to 22 to make 100?
78
Subtract 22 from 100: 100 − 22 = 78.
11. How many more do you need to add to 26 to make 50?
24
Subtract 26 from 50: 50 − 26 = 24.
12. How many more do you need to add to 21 to make 30?
9
Subtract 21 from 30: 30 − 21 = 9.

12 questions · Seed 104751 · 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 98 to make 100?
98 · 100 · Complements to 10, 20 & 100
2. How many more do you need to add to 3 to make 20?
3 · 20 · Complements to 10, 20 & 100
3. How many more do you need to add to 28 to make 50?
28 · 50 · Complements to 10, 20 & 100
4. How many more do you need to add to 27 to make 100?
27 · 100 · Complements to 10, 20 & 100
5. How many more do you need to add to 82 to make 100?
82 · 100 · Complements to 10, 20 & 100
6. How many more do you need to add to 18 to make 20?
18 · 20 · Complements to 10, 20 & 100
7. How many more do you need to add to 27 to make 50?
27 · 50 · Complements to 10, 20 & 100
8. How many more do you need to add to 33 to make 100?
33 · 100 · Complements to 10, 20 & 100
9. How many more do you need to add to 4 to make 30?
4 · 30 · Complements to 10, 20 & 100
10. How many more do you need to add to 22 to make 100?
22 · 100 · Complements to 10, 20 & 100
11. How many more do you need to add to 26 to make 50?
26 · 50 · Complements to 10, 20 & 100
12. How many more do you need to add to 21 to make 30?
21 · 30 · Complements to 10, 20 & 100

12 questions · Seed 104751 · 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 98 to make 100?
2
Subtract 98 from 100: 100 − 98 = 2.
2. How many more do you need to add to 3 to make 20?
17
Subtract 3 from 20: 20 − 3 = 17.
3. How many more do you need to add to 28 to make 50?
22
Subtract 28 from 50: 50 − 28 = 22.
4. How many more do you need to add to 27 to make 100?
73
Subtract 27 from 100: 100 − 27 = 73.
5. How many more do you need to add to 82 to make 100?
18
Subtract 82 from 100: 100 − 82 = 18.
6. How many more do you need to add to 18 to make 20?
2
Subtract 18 from 20: 20 − 18 = 2.
7. How many more do you need to add to 27 to make 50?
23
Subtract 27 from 50: 50 − 27 = 23.
8. How many more do you need to add to 33 to make 100?
67
Subtract 33 from 100: 100 − 33 = 67.
9. How many more do you need to add to 4 to make 30?
26
Subtract 4 from 30: 30 − 4 = 26.
10. How many more do you need to add to 22 to make 100?
78
Subtract 22 from 100: 100 − 22 = 78.
11. How many more do you need to add to 26 to make 50?
24
Subtract 26 from 50: 50 − 26 = 24.
12. How many more do you need to add to 21 to make 30?
9
Subtract 21 from 30: 30 − 21 = 9.

12 questions · Seed 104751 · Age guidance, not curriculum certification