Page 16 - Whole Numbers (Addition and Subtraction)

There are eight different ways to form 900 by adding two
multiples of hundred:
100 + 800 = 900 200 + 700 = 900
300 + 600 = 900 400 + 500 = 900

500 + 400 = 900 600 + 300 = 900
700 + 200 = 900 800 + 100 = 900

If you know that 300 + 600 = 900, you also know two subtraction
facts, namely 900 − 600 = 300 and 900 − 300 = 600.

14. Write all the other subtraction facts that you can know if you
know the different addition facts given above.

15. How much is each of the following?
(a) 900 − 400 (b) 900 − 600
(c) 1 000 − 600 (d) 1 000 − 400
(e) 800 − 300 (f) 700 − 300

(g) 1 000 − 300 (h) 600 − 200

3.6 Add and subtract with multiples of 10

1. Calculate each of the following. You may think of movements
on a number line and filling up to the nearest 100 to help you
to do this.
(a) 260 + 90 (b) 280 + 70

(c) 170 + 60 (d) 670 + 150

You need not draw a number line when you add by filling up. You
can just write as follows:
280 + 20 → 300 + 70 = 370, so 280 + 90 = 370

2. Calculate.
(a) 270 + 80 (b) 480 + 60

(c) 560 + 90 (d) 370 + 70

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