Step-by-step Maths Level 2: Related facts for a bond to 20
Part of the Step-by-step Maths Level 2 number bonds to 20 chapter. Chapter overview · whole chapter on one page
Related facts for a bond to 20
One bond gives four facts. For 6 and 14 make 20 there are two additions and two subtractions.
Use the same three numbers in every fact: 6, 14 and 20.
Key ideas
- 6 + 14 = 20 and 14 + 6 = 20.
- 20 - 6 = 14 and 20 - 14 = 6.
- Each fact uses the same three numbers.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.6 + 14 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 6 = 14
- Write the answer. The other part is the answer.14
Check. 6 + 14 = 20 and 20 - 6 = 14 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. Find the missing part of the addition.
- Look at the 14 we know. It is one of the two parts.14
- Count on or take away from 20. The missing part is the rest of 20.20 - 14 = 6
- Write the missing number. 6
Check. 14 + 6 = 20. It works.
Watch out. The whole is 20. The missing part is what is left after you take away the known part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.11 + 9 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 11 = 9
- Write the answer. The other part is the answer.9
Check. 11 + 9 = 20 and 20 - 11 = 9 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Watch out
Watch out. 20 - 6 is not the same as 6 - 20. Subtract the smaller part from the whole.
Exam tip
Grown-up tip. Write the fact family for each bond on a sticky note. Then cover one number and ask for it.
Exercise 4D Practice: related facts
Non-calculatorMethod. Find the missing part of the addition.
- Look at the 16 we know. It is one of the two parts.16
- Count on or take away from 20. The missing part is the rest of 20.20 - 16 = 4
- Write the missing number. 4
Check. 16 + 4 = 20. It works.
Watch out. The whole is 20. The missing part is what is left after you take away the known part.
Method. Find the missing part of the addition.
- Look at the 3 we know. It is one of the two parts.3
- Count on or take away from 20. The missing part is the rest of 20.20 - 3 = 17
- Write the missing number. 17
Check. 3 + 17 = 20. It works.
Watch out. The whole is 20. The missing part is what is left after you take away the known part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.19 + 1 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 19 = 1
- Write the answer. The other part is the answer.1
Check. 19 + 1 = 20 and 20 - 19 = 1 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.11 + 9 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 11 = 9
- Write the answer. The other part is the answer.9
Check. 11 + 9 = 20 and 20 - 11 = 9 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. Find the missing part of the addition.
- Look at the 18 we know. It is one of the two parts.18
- Count on or take away from 20. The missing part is the rest of 20.20 - 18 = 2
- Write the missing number. 2
Check. 18 + 2 = 20. It works.
Watch out. The whole is 20. The missing part is what is left after you take away the known part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.4 + 16 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 4 = 16
- Write the answer. The other part is the answer.16
Check. 4 + 16 = 20 and 20 - 4 = 16 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.3 + 17 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 3 = 17
- Write the answer. The other part is the answer.17
Check. 3 + 17 = 20 and 20 - 3 = 17 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.16 + 4 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 16 = 4
- Write the answer. The other part is the answer.4
Check. 16 + 4 = 20 and 20 - 16 = 4 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. Find the missing part of the addition.
- Look at the 19 we know. It is one of the two parts.19
- Count on or take away from 20. The missing part is the rest of 20.20 - 19 = 1
- Write the missing number. 1
Check. 19 + 1 = 20. It works.
Watch out. The whole is 20. The missing part is what is left after you take away the known part.
Method. Find the missing part of the addition.
- Look at the 2 we know. It is one of the two parts.2
- Count on or take away from 20. The missing part is the rest of 20.20 - 2 = 18
- Write the missing number. 18
Check. 2 + 18 = 20. It works.
Watch out. The whole is 20. The missing part is what is left after you take away the known part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.14 + 6 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 14 = 6
- Write the answer. The other part is the answer.6
Check. 14 + 6 = 20 and 20 - 14 = 6 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. Find the missing part of the addition.
- Look at the 14 we know. It is one of the two parts.14
- Count on or take away from 20. The missing part is the rest of 20.20 - 14 = 6
- Write the missing number. 6
Check. 14 + 6 = 20. It works.
Watch out. The whole is 20. The missing part is what is left after you take away the known part.
Method. Find the missing part of the addition.
- Look at the 11 we know. It is one of the two parts.11
- Count on or take away from 20. The missing part is the rest of 20.20 - 11 = 9
- Write the missing number. 9
Check. 11 + 9 = 20. It works.
Watch out. The whole is 20. The missing part is what is left after you take away the known part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.13 + 7 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 13 = 7
- Write the answer. The other part is the answer.7
Check. 13 + 7 = 20 and 20 - 13 = 7 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.6 + 14 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 6 = 14
- Write the answer. The other part is the answer.14
Check. 6 + 14 = 20 and 20 - 6 = 14 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.
Method. A fact family has an addition and a subtraction with the same numbers.
- Read the addition fact. It has two parts and a whole.7 + 13 = 20
- Use the whole, 20, to make the subtraction. Take one part away from the whole to find the other part.20 - 7 = 13
- Write the answer. The other part is the answer.13
Check. 7 + 13 = 20 and 20 - 7 = 13 use the same numbers.
Watch out. The subtraction takes away a part from the whole, so the answer is the other part.