Page 52 - Whole Numbers (Addition and Subtraction)

3. Calculate:

(a) The sum of 7 982 and 2 648
(b) The difference between 8 002 and 796

(c) The sum of 895, 6 853 and 9 342

(d) Add 1 021 to the difference between 7 178 and 3 099.
(e) Subtract 3 505 from 4 050 and add the difference to the
sum of 2 999 and 1 878.

(f) 3 784 + 2 737
(g) 7 243 − 3 569

It is often possible to replace a calculation with an easier
calculation that will produce the same answer.

For example, if you have to calculate 3 784 + 2 737 you can first
transfer 16 from 2 737 to 3 784, to fill it up to 3 800. Then you can
transfer 200 from the 2 721 that remains, to fill the 3 800 up to
4 000. Now you can calculate 4 000 + 2 521, which is much easier
than calculating 3 784 + 2 737.
16 200

3 784 + 2 737 = 3 800 + 2 721 = 4 000 + 2 521 = 6 521

If you have to calculate 7 243 − 3 569, you can add 31 to both
numbers to get 7 274 − 3 600. You can further add 400 to both
numbers to get 7 674 − 4 000. This is much easier to calculate
than 7 243 − 3 569, but will produce the same answer.
+ 31 + 400

7 243 − 3 569 = 7 274 − 3 600 = 7 674 − 4 000 = 3 674

+ 31 + 400

4. In each case, first make transfers so that the calculation is
replaced with an easier calculation.
(a) 3 403 + 2 265 (b) 7 259 + 2 135
(c) 3 459 + 2 265 (d) 7 259 + 1 875

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