Step-by-step Maths Level 2: Pairs that make 20
Part of the Step-by-step Maths Level 2 number bonds to 20 chapter. Chapter overview · whole chapter on one page
Pairs that make 20
A pair of numbers that makes 20 is called a bond to 20. For example, 13 and 7 make 20.
If you know one part, take it away from 20 to find the other part.
Key ideas
- A bond to 20 has two parts that add up to 20.
- The parts can be turned round: 7 and 13 also make 20.
- Take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 13. It is the part we know.13
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 13 = 7
- Write the answer. This is the other part of the bond.7
Check. 13 + 7 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 8. It is the part we know.8
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 8 = 12
- Write the answer. This is the other part of the bond.12
Check. 8 + 12 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 17. It is the part we know.17
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 17 = 3
- Write the answer. This is the other part of the bond.3
Check. 17 + 3 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Watch out
Watch out. The whole is 20, not 10. Do not stop at 10 when you count on.
Exam tip
Grown-up tip. Use 20 counters split into two cups. Ask: “How many in the other cup?”
Exercise 4A Practice: pairs that make 20
Non-calculatorMethod. Find the part that makes 20 with the number we know.
- Start with 9. It is the part we know.9
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 9 = 11
- Write the answer. This is the other part of the bond.11
Check. 9 + 11 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 18. It is the part we know.18
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 18 = 2
- Write the answer. This is the other part of the bond.2
Check. 18 + 2 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 13. It is the part we know.13
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 13 = 7
- Write the answer. This is the other part of the bond.7
Check. 13 + 7 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 16. It is the part we know.16
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 16 = 4
- Write the answer. This is the other part of the bond.4
Check. 16 + 4 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 8. It is the part we know.8
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 8 = 12
- Write the answer. This is the other part of the bond.12
Check. 8 + 12 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 12. It is the part we know.12
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 12 = 8
- Write the answer. This is the other part of the bond.8
Check. 12 + 8 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 15. It is the part we know.15
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 15 = 5
- Write the answer. This is the other part of the bond.5
Check. 15 + 5 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 19. It is the part we know.19
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 19 = 1
- Write the answer. This is the other part of the bond.1
Check. 19 + 1 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 2. It is the part we know.2
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 2 = 18
- Write the answer. This is the other part of the bond.18
Check. 2 + 18 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 6. It is the part we know.6
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 6 = 14
- Write the answer. This is the other part of the bond.14
Check. 6 + 14 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 10. It is the part we know.10
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 10 = 10
- Write the answer. This is the other part of the bond.10
Check. 10 + 10 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 4. It is the part we know.4
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 4 = 16
- Write the answer. This is the other part of the bond.16
Check. 4 + 16 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 14. It is the part we know.14
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 14 = 6
- Write the answer. This is the other part of the bond.6
Check. 14 + 6 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 3. It is the part we know.3
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 3 = 17
- Write the answer. This is the other part of the bond.17
Check. 3 + 17 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 1. It is the part we know.1
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 1 = 19
- Write the answer. This is the other part of the bond.19
Check. 1 + 19 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.
Method. Find the part that makes 20 with the number we know.
- Start with 11. It is the part we know.11
- Find how far it is to 20. Take the known part away from the whole, 20.20 - 11 = 9
- Write the answer. This is the other part of the bond.9
Check. 11 + 9 = 20. It works.
Watch out. The whole is 20, so take the known part away from 20.