*This quiz addresses the requirements of the National Curriculum KS1 Maths and Numeracy for children aged 6 and 7 in year 2. Specifically this quiz is aimed at the section dealing with knowing number facts to 20. *

Knowing addition and subtraction facts (or number facts) to 20 by heart means being able to quickly know the pairs of numbers which make a total of twenty, as well as the associated subtraction facts. For example, if you know that 13 + 7 = 20, then you should also recognise that 20 - 13 = 7 or 20 - 7 = 13.

Question 1

Which of the following pairs of number do not add up to give 20?

9 + 11

2 + 18

16 + 5

20 + 0

16 + 5 = 21

Question 2

Which three pairs of numbers all add up to 20?

19 + 1

17 + 3

5 + 15

17 + 3

5 + 15

12 + 9

11 + 7

3 + 16

11 + 7

3 + 16

7 + 20

6 + 12

7 + 19

6 + 12

7 + 19

4 + 12

16 + 8

20 + 1

16 + 8

20 + 1

All the others add up to different numbers

Question 3

Which three other facts go with 16 + 4 = 20?

20 + 16 = 4

20 + 4 = 16

16 - 20 = 4

20 + 4 = 16

16 - 20 = 4

16 - 20 = 4

4 - 20 = 16

20 + 16 = 4

4 - 20 = 16

20 + 16 = 4

4 + 16 = 20

16 - 4 = 20

4 - 16 = 20

16 - 4 = 20

4 - 16 = 20

4 + 16 = 20

20 - 16 = 4

20 - 4 = 16

20 - 16 = 4

20 - 4 = 16

For the subtraction facts, the largest number should be at the beginning

Question 4

Which of the following is true?

12 - 20 = 8

20 - 2 = 18

8 + 20 = 12

18 + 20 = 2

20 - 18 = 2 is the other subtraction fact for these numbers

Question 5

If you know that 14 + 6 = 20, what else do you know?

20 + 14 = 6

20 - 14 = 6

14 - 20 = 6

6 - 14 = 20

You would also know that 20 - 6 = 14

Question 6

Which number fact is incorrect?

11 + 9 = 20

9 + 11 = 20

20 - 9 = 11

11 - 20 = 9

11 - 20 gives a negative answer of -9!

Question 7

Which 'family' of facts is incorrect?

2 + 18 = 20

18 + 2 = 20

20 - 18 = 2

20 - 2 = 18

18 + 2 = 20

20 - 18 = 2

20 - 2 = 18

16 + 5 = 20

5 + 16 = 20

20 - 16 = 5

20 - 5 = 16

5 + 16 = 20

20 - 16 = 5

20 - 5 = 16

5 + 15 = 20

15 + 5 = 20

20 - 5 = 15

20 - 15 = 5

15 + 5 = 20

20 - 5 = 15

20 - 15 = 5

10 + 10 = 20

20 - 10 = 10

20 - 10 = 10

16 + 5 = 21, not 20 so all the other facts must be incorrect too

Question 8

Which of the following is true?

2 + 18 = 20 so 20 + 18 = 2

2 + 18 = 20 so 18 + 2 = 20

2 + 18 = 20 so 20 + 2 = 18

2 + 18 = 20 so 18 + 20 = 2

Adding the two smaller numbers in any order gives the larger number

Question 9

Which number is missing: 17 + ? = 20

5

3

7

9

17 + 3 = 20 and so 3 + 17 = 20 also

Question 10

Which 'family' of facts is incorrect?

7 + 13 = 20

13 + 7 = 20

20 - 13 = 7

20 - 7 = 13

13 + 7 = 20

20 - 13 = 7

20 - 7 = 13

8 + 12 = 20

12 + 8 = 20

20 - 8 = 12

20 - 12 = 8

12 + 8 = 20

20 - 8 = 12

20 - 12 = 8

9 + 11 = 20

11 + 9 = 20

20 - 11 = 9

20 - 9 = 11

11 + 9 = 20

20 - 11 = 9

20 - 9 = 11

4 + 14 = 20

14 + 4 = 20

20 - 4 = 14

20 - 14 = 4

14 + 4 = 20

20 - 4 = 14

20 - 14 = 4

14 + 4 = 18, so all the other facts must be incorrect too