Chapter 3.3 (Mathematics 5)

Estimating difference by rounding off numbers to the nearest hundreds

Estimating difference by rounding off numbers to the nearest hundreds

Group Activity 3

In groups of three:

Use a number line to find the estimate difference of 6 549 and 6 052.

  1. Draw a number line and mark equal spaces as shown:
  1. Show the position 6 052 and 6 549.
  2. Use the number line to round off each number to the nearest 100. Circle the numbers.
  3. Obtain the estimate difference.
  4. Discuss your results and share with other groups.

Example 3

Use a number line to find the estimate difference of 16 280 and 15 450.

16 280 to the nearest hundred is 16 300.

15 450 to the nearest hundred is 15 500.

Exercise C

C1

In pairs, use a number line to find the estimate difference in each of the following:

  1. 349 – 125
  2. 6 568 – 6 345
  3. 25 350 – 24 850
  • 3 600
  • 2 200
  • 3 200
  • 2 400
  • 6 349 – 2 712
  • 5 684 – 3 459
  • 6 747 – 3 467
  • 3 936 – 1 474

C3

There were 56 982 tea bushes in a farm. Some more tea bushes were planted. The total number of tea bushes was 82 495. Estimate the difference by rounding off the numbers to the nearest hundreds.

C4

Two towns had 4 878 and 5 639 children immunised against polio. Estimate the difference by rounding off the numbers to the nearest hundreds.

C5

There were 59 799 bags of wheat in a store. The owner sold 45 927 bags of the wheat. Estimate the difference by rounding off the numbers to the nearest hundreds.