Page 21 - Whole Numbers (Addition and Subtraction)

6. A farmer has 734 cows. A veldfire breaks out and 568 of the
cows are killed. Approximately how many cows are left?

7. Do questions 5 and 6 again, but this time round off the
numbers to the nearest ten before you calculate.
8. Mrs Tshabalala wrote the prices of items 47
she bought on a paper slip. 132
Round off each price to the nearest ten 34
rand. 74
Then estimate the total by adding the 58
rounded-off prices. 58
198
66

To calculate 78 + 64 you can first round off to the nearest ten
and get an approximate answer: 80 + 60 = 140.
Then you can compensate to get the accurate answer:
140 − 2 + 4 = 142.

9. Compensate to get the accurate answers for questions 5, 6 and 8.

3.8 Break down and build up numbers

To add numbers, it helps to break them down into place value
parts first. For example, when you have to calculate 364 + 588,
the numbers may be taken apart like this:
4 60
364: 300
80 8 500
588:

The hundreds can be added to the hundreds, the tens to the tens
and the ones to the ones:
300 + 500 = 800 60 + 80 = 140 4 + 8 = 12
So, 364 + 588 = 800 + 140 + 12

1. Write 800 + 140 + 12 as a single number.

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