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 3 to make 20?
3 · 20 · Complements to 10, 20 & 100
2. How many more do you need to add to 7 to make 100?
7 · 100 · Complements to 10, 20 & 100
3. How many more do you need to add to 18 to make 20?
18 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 28 to make 30?
28 · 30 · Complements to 10, 20 & 100
5. How many more do you need to add to 21 to make 50?
21 · 50 · Complements to 10, 20 & 100
6. How many more do you need to add to 6 to make 30?
6 · 30 · Complements to 10, 20 & 100
7. How many more do you need to add to 5 to make 20?
5 · 20 · Complements to 10, 20 & 100
8. How many more do you need to add to 2 to make 50?
2 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 14 to make 20?
14 · 20 · Complements to 10, 20 & 100
10. How many more do you need to add to 2 to make 20?
2 · 20 · Complements to 10, 20 & 100
11. How many more do you need to add to 34 to make 50?
34 · 50 · Complements to 10, 20 & 100
12. How many more do you need to add to 15 to make 20?
15 · 20 · Complements to 10, 20 & 100

12 questions · Seed 104770 · 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 3 to make 20?
17
Subtract 3 from 20: 20 − 3 = 17.
2. How many more do you need to add to 7 to make 100?
93
Subtract 7 from 100: 100 − 7 = 93.
3. How many more do you need to add to 18 to make 20?
2
Subtract 18 from 20: 20 − 18 = 2.
4. How many more do you need to add to 28 to make 30?
2
Subtract 28 from 30: 30 − 28 = 2.
5. How many more do you need to add to 21 to make 50?
29
Subtract 21 from 50: 50 − 21 = 29.
6. How many more do you need to add to 6 to make 30?
24
Subtract 6 from 30: 30 − 6 = 24.
7. How many more do you need to add to 5 to make 20?
15
Subtract 5 from 20: 20 − 5 = 15.
8. How many more do you need to add to 2 to make 50?
48
Subtract 2 from 50: 50 − 2 = 48.
9. How many more do you need to add to 14 to make 20?
6
Subtract 14 from 20: 20 − 14 = 6.
10. How many more do you need to add to 2 to make 20?
18
Subtract 2 from 20: 20 − 2 = 18.
11. How many more do you need to add to 34 to make 50?
16
Subtract 34 from 50: 50 − 34 = 16.
12. How many more do you need to add to 15 to make 20?
5
Subtract 15 from 20: 20 − 15 = 5.

12 questions · Seed 104770 · 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 3 to make 20?
3 · 20 · Complements to 10, 20 & 100
2. How many more do you need to add to 7 to make 100?
7 · 100 · Complements to 10, 20 & 100
3. How many more do you need to add to 18 to make 20?
18 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 28 to make 30?
28 · 30 · Complements to 10, 20 & 100
5. How many more do you need to add to 21 to make 50?
21 · 50 · Complements to 10, 20 & 100
6. How many more do you need to add to 6 to make 30?
6 · 30 · Complements to 10, 20 & 100
7. How many more do you need to add to 5 to make 20?
5 · 20 · Complements to 10, 20 & 100
8. How many more do you need to add to 2 to make 50?
2 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 14 to make 20?
14 · 20 · Complements to 10, 20 & 100
10. How many more do you need to add to 2 to make 20?
2 · 20 · Complements to 10, 20 & 100
11. How many more do you need to add to 34 to make 50?
34 · 50 · Complements to 10, 20 & 100
12. How many more do you need to add to 15 to make 20?
15 · 20 · Complements to 10, 20 & 100

12 questions · Seed 104770 · 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 3 to make 20?
17
Subtract 3 from 20: 20 − 3 = 17.
2. How many more do you need to add to 7 to make 100?
93
Subtract 7 from 100: 100 − 7 = 93.
3. How many more do you need to add to 18 to make 20?
2
Subtract 18 from 20: 20 − 18 = 2.
4. How many more do you need to add to 28 to make 30?
2
Subtract 28 from 30: 30 − 28 = 2.
5. How many more do you need to add to 21 to make 50?
29
Subtract 21 from 50: 50 − 21 = 29.
6. How many more do you need to add to 6 to make 30?
24
Subtract 6 from 30: 30 − 6 = 24.
7. How many more do you need to add to 5 to make 20?
15
Subtract 5 from 20: 20 − 5 = 15.
8. How many more do you need to add to 2 to make 50?
48
Subtract 2 from 50: 50 − 2 = 48.
9. How many more do you need to add to 14 to make 20?
6
Subtract 14 from 20: 20 − 14 = 6.
10. How many more do you need to add to 2 to make 20?
18
Subtract 2 from 20: 20 − 2 = 18.
11. How many more do you need to add to 34 to make 50?
16
Subtract 34 from 50: 50 − 34 = 16.
12. How many more do you need to add to 15 to make 20?
5
Subtract 15 from 20: 20 − 15 = 5.

12 questions · Seed 104770 · Age guidance, not curriculum certification