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 21 to make 50?
21 · 50 · Complements to 10, 20 & 100
2. How many more do you need to add to 30 to make 100?
30 · 100 · Complements to 10, 20 & 100
3. How many more do you need to add to 12 to make 20?
12 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 1 to make 30?
1 · 30 · Complements to 10, 20 & 100
5. How many more do you need to add to 47 to make 100?
47 · 100 · Complements to 10, 20 & 100
6. How many more do you need to add to 5 to make 20?
5 · 20 · Complements to 10, 20 & 100
7. How many more do you need to add to 15 to make 30?
15 · 30 · Complements to 10, 20 & 100
8. How many more do you need to add to 6 to make 50?
6 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 42 to make 50?
42 · 50 · Complements to 10, 20 & 100
10. How many more do you need to add to 7 to make 30?
7 · 30 · Complements to 10, 20 & 100
11. How many more do you need to add to 23 to make 50?
23 · 50 · Complements to 10, 20 & 100
12. How many more do you need to add to 14 to make 20?
14 · 20 · Complements to 10, 20 & 100

12 questions · Seed 104789 · 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 21 to make 50?
29
Subtract 21 from 50: 50 − 21 = 29.
2. How many more do you need to add to 30 to make 100?
70
Subtract 30 from 100: 100 − 30 = 70.
3. How many more do you need to add to 12 to make 20?
8
Subtract 12 from 20: 20 − 12 = 8.
4. How many more do you need to add to 1 to make 30?
29
Subtract 1 from 30: 30 − 1 = 29.
5. How many more do you need to add to 47 to make 100?
53
Subtract 47 from 100: 100 − 47 = 53.
6. How many more do you need to add to 5 to make 20?
15
Subtract 5 from 20: 20 − 5 = 15.
7. How many more do you need to add to 15 to make 30?
15
Subtract 15 from 30: 30 − 15 = 15.
8. How many more do you need to add to 6 to make 50?
44
Subtract 6 from 50: 50 − 6 = 44.
9. How many more do you need to add to 42 to make 50?
8
Subtract 42 from 50: 50 − 42 = 8.
10. How many more do you need to add to 7 to make 30?
23
Subtract 7 from 30: 30 − 7 = 23.
11. How many more do you need to add to 23 to make 50?
27
Subtract 23 from 50: 50 − 23 = 27.
12. How many more do you need to add to 14 to make 20?
6
Subtract 14 from 20: 20 − 14 = 6.

12 questions · Seed 104789 · 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 21 to make 50?
21 · 50 · Complements to 10, 20 & 100
2. How many more do you need to add to 30 to make 100?
30 · 100 · Complements to 10, 20 & 100
3. How many more do you need to add to 12 to make 20?
12 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 1 to make 30?
1 · 30 · Complements to 10, 20 & 100
5. How many more do you need to add to 47 to make 100?
47 · 100 · Complements to 10, 20 & 100
6. How many more do you need to add to 5 to make 20?
5 · 20 · Complements to 10, 20 & 100
7. How many more do you need to add to 15 to make 30?
15 · 30 · Complements to 10, 20 & 100
8. How many more do you need to add to 6 to make 50?
6 · 50 · Complements to 10, 20 & 100
9. How many more do you need to add to 42 to make 50?
42 · 50 · Complements to 10, 20 & 100
10. How many more do you need to add to 7 to make 30?
7 · 30 · Complements to 10, 20 & 100
11. How many more do you need to add to 23 to make 50?
23 · 50 · Complements to 10, 20 & 100
12. How many more do you need to add to 14 to make 20?
14 · 20 · Complements to 10, 20 & 100

12 questions · Seed 104789 · 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 21 to make 50?
29
Subtract 21 from 50: 50 − 21 = 29.
2. How many more do you need to add to 30 to make 100?
70
Subtract 30 from 100: 100 − 30 = 70.
3. How many more do you need to add to 12 to make 20?
8
Subtract 12 from 20: 20 − 12 = 8.
4. How many more do you need to add to 1 to make 30?
29
Subtract 1 from 30: 30 − 1 = 29.
5. How many more do you need to add to 47 to make 100?
53
Subtract 47 from 100: 100 − 47 = 53.
6. How many more do you need to add to 5 to make 20?
15
Subtract 5 from 20: 20 − 5 = 15.
7. How many more do you need to add to 15 to make 30?
15
Subtract 15 from 30: 30 − 15 = 15.
8. How many more do you need to add to 6 to make 50?
44
Subtract 6 from 50: 50 − 6 = 44.
9. How many more do you need to add to 42 to make 50?
8
Subtract 42 from 50: 50 − 42 = 8.
10. How many more do you need to add to 7 to make 30?
23
Subtract 7 from 30: 30 − 7 = 23.
11. How many more do you need to add to 23 to make 50?
27
Subtract 23 from 50: 50 − 23 = 27.
12. How many more do you need to add to 14 to make 20?
6
Subtract 14 from 20: 20 − 14 = 6.

12 questions · Seed 104789 · Age guidance, not curriculum certification