Chapter 3.4 (Mathematics 5)

Estimating differences by rounding off numbers to the nearest thousand

Estimating differences by rounding off numbers to the nearest thousand

Group Activity 4

In groups:

  1. Write two 6-digit numbers.
  2. Round off each number to the nearest thousand.
  3. Find the estimate difference.
  4. Discuss the results with other groups.

Example 4

Work out the estimate difference of 675 382 – 438 644 by rounding off each of the numbers to the nearest thousand.
  • 675 382 is 675 000 to the nearest thousand.
  • 438 644 is 439 000 to the nearest thousand.
  • 675 000 – 439 000 = 236 000.

The estimate difference is 236 000.

Exercise D

  1. 78 935 – 67 595
     –  = 
  2. 86 846 – 54 982
     –  = 
  3. 493 784 – 8 967
     –  = 
  4. 834 967 – 87 349
     –  = 

   = 

D3

There were 89 650 litres of petrol in a petrol station at the start of a week. By the end of the week 63 241 litres of the petrol had been sold. By rounding off the numbers to the nearest thousand, find the estimate difference of the amount of petrol that remained.

D4

A dairy company had 275 389 packets of milk. The company donated 59 850 packets to children homes. Round off each number of packets to the nearest thousand and find the estimate difference of number of packets that remained.

   =