Page 4 - Whole Numbers (Addition and Subtraction)

6. Copy and complete the number sentences. Do not count!
(a) 3 + 7 = . . . (b) 3 + 8 = . . .
(c) 11 − 3 = . . . (d) 11 − 8 = . . .

7. Ma Susan is collecting her hens’ eggs.
She knows that if she finds 6 eggs + 6 = 44
more, she will have 44 eggs in total
in her basket.

To her surprise Ma Susan finds 9 eggs more, not only 6. How
many eggs does she now have in total?

3.2 Add without counting

If you always have to count to find facts like 7 + 5 = 12, it will
always take you very long to do calculations. You have to learn to
make addition and subtraction facts without counting!
A good way to do that is to make new facts from facts that you
already know. For example if you know that 35 + 2 = 37, it is easy
to know that 35 + 3 = 38, because it is just 1 more.
In this section you will learn different ways to form new facts
from facts that you already know.

1. You know that 10 + 10 = 20.
Try to use this fact to quickly find the answers to the
following. Start from 10 + 10 = 20 in each case.
(a) 8 + 12 (b) 10 + 13

(c) 9 + 11 (d) 7 + 13

An easy way to make a new addition fact from a fact that you
know, is to shift part of one number to the other number, for
example:
3

10 + 20 = 30
By shifting 3 from the 20 to the 10, you get the new fact 13 + 17 = 30.

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