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 20 to make 50?
20 · 50 · Complements to 10, 20 & 100
2. How many more do you need to add to 18 to make 20?
18 · 20 · Complements to 10, 20 & 100
3. How many more do you need to add to 10 to make 100?
10 · 100 · Complements to 10, 20 & 100
4. How many more do you need to add to 23 to make 30?
23 · 30 · Complements to 10, 20 & 100
5. How many more do you need to add to 33 to make 100?
33 · 100 · Complements to 10, 20 & 100
6. How many more do you need to add to 42 to make 50?
42 · 50 · Complements to 10, 20 & 100
7. How many more do you need to add to 8 to make 100?
8 · 100 · Complements to 10, 20 & 100
8. How many more do you need to add to 15 to make 30?
15 · 30 · Complements to 10, 20 & 100
9. How many more do you need to add to 83 to make 100?
83 · 100 · Complements to 10, 20 & 100
10. How many more do you need to add to 2 to make 50?
2 · 50 · Complements to 10, 20 & 100
11. How many more do you need to add to 7 to make 20?
7 · 20 · Complements to 10, 20 & 100
12. How many more do you need to add to 35 to make 50?
35 · 50 · Complements to 10, 20 & 100

12 questions · Seed 104753 · 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 20 to make 50?
30
Subtract 20 from 50: 50 − 20 = 30.
2. How many more do you need to add to 18 to make 20?
2
Subtract 18 from 20: 20 − 18 = 2.
3. How many more do you need to add to 10 to make 100?
90
Subtract 10 from 100: 100 − 10 = 90.
4. How many more do you need to add to 23 to make 30?
7
Subtract 23 from 30: 30 − 23 = 7.
5. How many more do you need to add to 33 to make 100?
67
Subtract 33 from 100: 100 − 33 = 67.
6. How many more do you need to add to 42 to make 50?
8
Subtract 42 from 50: 50 − 42 = 8.
7. How many more do you need to add to 8 to make 100?
92
Subtract 8 from 100: 100 − 8 = 92.
8. How many more do you need to add to 15 to make 30?
15
Subtract 15 from 30: 30 − 15 = 15.
9. How many more do you need to add to 83 to make 100?
17
Subtract 83 from 100: 100 − 83 = 17.
10. How many more do you need to add to 2 to make 50?
48
Subtract 2 from 50: 50 − 2 = 48.
11. How many more do you need to add to 7 to make 20?
13
Subtract 7 from 20: 20 − 7 = 13.
12. How many more do you need to add to 35 to make 50?
15
Subtract 35 from 50: 50 − 35 = 15.

12 questions · Seed 104753 · 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 20 to make 50?
20 · 50 · Complements to 10, 20 & 100
2. How many more do you need to add to 18 to make 20?
18 · 20 · Complements to 10, 20 & 100
3. How many more do you need to add to 10 to make 100?
10 · 100 · Complements to 10, 20 & 100
4. How many more do you need to add to 23 to make 30?
23 · 30 · Complements to 10, 20 & 100
5. How many more do you need to add to 33 to make 100?
33 · 100 · Complements to 10, 20 & 100
6. How many more do you need to add to 42 to make 50?
42 · 50 · Complements to 10, 20 & 100
7. How many more do you need to add to 8 to make 100?
8 · 100 · Complements to 10, 20 & 100
8. How many more do you need to add to 15 to make 30?
15 · 30 · Complements to 10, 20 & 100
9. How many more do you need to add to 83 to make 100?
83 · 100 · Complements to 10, 20 & 100
10. How many more do you need to add to 2 to make 50?
2 · 50 · Complements to 10, 20 & 100
11. How many more do you need to add to 7 to make 20?
7 · 20 · Complements to 10, 20 & 100
12. How many more do you need to add to 35 to make 50?
35 · 50 · Complements to 10, 20 & 100

12 questions · Seed 104753 · 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 20 to make 50?
30
Subtract 20 from 50: 50 − 20 = 30.
2. How many more do you need to add to 18 to make 20?
2
Subtract 18 from 20: 20 − 18 = 2.
3. How many more do you need to add to 10 to make 100?
90
Subtract 10 from 100: 100 − 10 = 90.
4. How many more do you need to add to 23 to make 30?
7
Subtract 23 from 30: 30 − 23 = 7.
5. How many more do you need to add to 33 to make 100?
67
Subtract 33 from 100: 100 − 33 = 67.
6. How many more do you need to add to 42 to make 50?
8
Subtract 42 from 50: 50 − 42 = 8.
7. How many more do you need to add to 8 to make 100?
92
Subtract 8 from 100: 100 − 8 = 92.
8. How many more do you need to add to 15 to make 30?
15
Subtract 15 from 30: 30 − 15 = 15.
9. How many more do you need to add to 83 to make 100?
17
Subtract 83 from 100: 100 − 83 = 17.
10. How many more do you need to add to 2 to make 50?
48
Subtract 2 from 50: 50 − 2 = 48.
11. How many more do you need to add to 7 to make 20?
13
Subtract 7 from 20: 20 − 7 = 13.
12. How many more do you need to add to 35 to make 50?
15
Subtract 35 from 50: 50 − 35 = 15.

12 questions · Seed 104753 · Age guidance, not curriculum certification