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 19 to make 100?
19 · 100 · Complements to 10, 20 & 100
2. How many more do you need to add to 42 to make 50?
42 · 50 · Complements to 10, 20 & 100
3. How many more do you need to add to 7 to make 20?
7 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 13 to make 50?
13 · 50 · Complements to 10, 20 & 100
5. How many more do you need to add to 40 to make 50?
40 · 50 · Complements to 10, 20 & 100
6. How many more do you need to add to 39 to make 50?
39 · 50 · Complements to 10, 20 & 100
7. How many more do you need to add to 16 to make 30?
16 · 30 · Complements to 10, 20 & 100
8. How many more do you need to add to 16 to make 20?
16 · 20 · Complements to 10, 20 & 100
9. How many more do you need to add to 97 to make 100?
97 · 100 · Complements to 10, 20 & 100
10. How many more do you need to add to 49 to make 100?
49 · 100 · Complements to 10, 20 & 100
11. How many more do you need to add to 12 to make 20?
12 · 20 · Complements to 10, 20 & 100
12. How many more do you need to add to 2 to make 20?
2 · 20 · Complements to 10, 20 & 100

12 questions · Seed 104733 · 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 19 to make 100?
81
Subtract 19 from 100: 100 − 19 = 81.
2. How many more do you need to add to 42 to make 50?
8
Subtract 42 from 50: 50 − 42 = 8.
3. How many more do you need to add to 7 to make 20?
13
Subtract 7 from 20: 20 − 7 = 13.
4. How many more do you need to add to 13 to make 50?
37
Subtract 13 from 50: 50 − 13 = 37.
5. How many more do you need to add to 40 to make 50?
10
Subtract 40 from 50: 50 − 40 = 10.
6. How many more do you need to add to 39 to make 50?
11
Subtract 39 from 50: 50 − 39 = 11.
7. How many more do you need to add to 16 to make 30?
14
Subtract 16 from 30: 30 − 16 = 14.
8. How many more do you need to add to 16 to make 20?
4
Subtract 16 from 20: 20 − 16 = 4.
9. How many more do you need to add to 97 to make 100?
3
Subtract 97 from 100: 100 − 97 = 3.
10. How many more do you need to add to 49 to make 100?
51
Subtract 49 from 100: 100 − 49 = 51.
11. How many more do you need to add to 12 to make 20?
8
Subtract 12 from 20: 20 − 12 = 8.
12. How many more do you need to add to 2 to make 20?
18
Subtract 2 from 20: 20 − 2 = 18.

12 questions · Seed 104733 · 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 19 to make 100?
19 · 100 · Complements to 10, 20 & 100
2. How many more do you need to add to 42 to make 50?
42 · 50 · Complements to 10, 20 & 100
3. How many more do you need to add to 7 to make 20?
7 · 20 · Complements to 10, 20 & 100
4. How many more do you need to add to 13 to make 50?
13 · 50 · Complements to 10, 20 & 100
5. How many more do you need to add to 40 to make 50?
40 · 50 · Complements to 10, 20 & 100
6. How many more do you need to add to 39 to make 50?
39 · 50 · Complements to 10, 20 & 100
7. How many more do you need to add to 16 to make 30?
16 · 30 · Complements to 10, 20 & 100
8. How many more do you need to add to 16 to make 20?
16 · 20 · Complements to 10, 20 & 100
9. How many more do you need to add to 97 to make 100?
97 · 100 · Complements to 10, 20 & 100
10. How many more do you need to add to 49 to make 100?
49 · 100 · Complements to 10, 20 & 100
11. How many more do you need to add to 12 to make 20?
12 · 20 · Complements to 10, 20 & 100
12. How many more do you need to add to 2 to make 20?
2 · 20 · Complements to 10, 20 & 100

12 questions · Seed 104733 · 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 19 to make 100?
81
Subtract 19 from 100: 100 − 19 = 81.
2. How many more do you need to add to 42 to make 50?
8
Subtract 42 from 50: 50 − 42 = 8.
3. How many more do you need to add to 7 to make 20?
13
Subtract 7 from 20: 20 − 7 = 13.
4. How many more do you need to add to 13 to make 50?
37
Subtract 13 from 50: 50 − 13 = 37.
5. How many more do you need to add to 40 to make 50?
10
Subtract 40 from 50: 50 − 40 = 10.
6. How many more do you need to add to 39 to make 50?
11
Subtract 39 from 50: 50 − 39 = 11.
7. How many more do you need to add to 16 to make 30?
14
Subtract 16 from 30: 30 − 16 = 14.
8. How many more do you need to add to 16 to make 20?
4
Subtract 16 from 20: 20 − 16 = 4.
9. How many more do you need to add to 97 to make 100?
3
Subtract 97 from 100: 100 − 97 = 3.
10. How many more do you need to add to 49 to make 100?
51
Subtract 49 from 100: 100 − 49 = 51.
11. How many more do you need to add to 12 to make 20?
8
Subtract 12 from 20: 20 − 12 = 8.
12. How many more do you need to add to 2 to make 20?
18
Subtract 2 from 20: 20 − 2 = 18.

12 questions · Seed 104733 · Age guidance, not curriculum certification