1. 4 number facts + -
Know 1 fact know 4

2. = – – = = + + = Learn one, know four 4 + 16 = 20 20 – 16 = 4
Each number sentence can be written in four ways. 20 20 20 20 = – – =
= 20
20 – 16 = 4
20 – 4 = 16
= 20 16 16 16 16 4 4 4 4 = + + =

3. Learn one, know four 20 – 12 = 8 20 – 12 = 8 20 – 14 = 6 20 – 14 = 6
Can you fill in the gaps?
20 – 12 = 8
20 – 12 = 8
20 – 14 = 6
20 – 14 = 6
20 – 8 = 12
20 – 8 = 12
20 – 6 = 14
20 – 6 = 14
= 20
= 20
= 20
= 20
= 20
= 20
= 20
= 20

4. Learn one, know four

5. Learn one, know four 16 – 7 = 9 16 – 7 = 9 16 – 9 = 7 16 – 9 = 7
When you learn one number fact, you are really learning four.
What is the missing figure
in these?
If we learn…
9 + 5 = 14
9 + 7 = 16
9 + 7 = 16
Then we also know…
5 + 9 = 14
14 – 9 = 5
14 – 5 = 9
7 + 9 = 16
7 + 9 = 16
16 – 7 = 9
16 – 7 = 9
16 – 9 = 7
16 – 9 = 7

6. Learn one, know four