Page 5 - Whole Numbers (Addition and Subtraction)

2. (a) Shift 5 from the one 20 to the other 20 to make a new fact
from 20 + 20 = 40.

(b) Shift 3 to make another fact from 20 + 20 = 40.

(c) Make three more facts from 20 + 20 = 40.
3. (a) Make three different facts from 10 + 5 = 15.

(b) Make three different facts from 10 + 7 = 17.

The examples below show another way how you can use an
addition fact that you already know to build other addition facts.

15 + 15 = 30 15 + 15 = 30 15 + 15 = 30

+ 1 + 1 + 2 − 1 − 1 + 3 − 1 + 2

16 + 16 = 32 14 + 15 = 29 18 + 14 = 32

4. Start with 20 + 10 = 30 and make ten other addition facts, all
with answers different than 30.

5. Zweli knows that 8 + 8 = 16.
How can he use this knowledge to find out how much 6 + 9 is?

Here is a different way to find addition facts.
To find out how much 37 + 8 is, you can fill up to 40 and then
add what remains of the 8:

30 40 50

You can describe your thinking by using an arrow:
37 + 3 → 40 + 5 = 45

By first adding 3 and then adding 5 you have added 8 in total.

6. Use arrows to show how 16 + 9 and 28 + 7 can be calculated by
filling up to 20 and 30.

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