Page 31 - Whole Numbers (Addition and Subtraction)

Subtract by adding on
Subtraction can also be done by filling up multiples of 10, 100
and 1 000.
For example, 7 234 − 4 876 can be calculated by finding out how
much should be added to 4 876 to reach 7 234, as shown below.

We add on in steps from 4 876 until we reach 7 234, and then
check how much we had to add on in total:

4 876 + 24 → 4 900 + 100 → 5 000 + 2 234 = 7 234.

In total we added on 24 + 100 + 2 234 which is 2 358.

So, 4 876 + 2 358 = 7 234 and 7 234 − 4 876 = 2 358.

3. Use the add-on method of subtraction to calculate the
following.
(a) 7 236 − 2 875 (b) 6 721 − 4 503
(c) 9 000 − 1 234 (d) 8 187 − 5 592
(e) 7 386 − 3 163 (f) 8 396 − 5 273

Add by adding on place value parts

To calculate 3 465 + 4 574 the number that is to be added can be
broken down into its place value parts. The place value parts can
then be added one by one to the first number:
4 574 = 4 000 + 500 + 70 + 4

So, 3 465 + 4 574 = 3 465 + 4 000 + 500 + 70 + 4 and it can be
calculated like this:

3 465 + 4 000 = 7 465
7 465 + 500 = 7 965
7 965 + 70 = 8 035

8 035 + 4 = 8 039

The work can also be shown like this:
3 465 + 4 000 → 7 465 + 500 → 7 965 + 70 → 8 035 + 4 = 8 039

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