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It is another part where we approximate before we calculate certain operation such as 45 x 68, 4.65 x 87.2 and some like that.

How do we approximate? And what are the rules?

It is simple,

For all whole numbers approximate to the nearest large value such as 45667 to ten thousands to become 50000, 45 to the nearest tens to become 50 and 522 to hundreds to become 500.

For decimals use some tricks to make your number very simple such as 12.5 to one significant figure to become 10, 0.0085 to three decimal places to become 0.009.

Example 1

Estimate the value of 256 x 65


256 to the nearest hundreds is 300 and 65 to the nearest tens is 70 then our new application becomes:

300 x 70 = 21000.

Example 2

Estimate the value of 5.6 x 0.65


5.6 to the nearest ones or one significant figure is 6 and 0.65 to the nearest ones is 1 then our new application becomes:

6 x 1 = 6.

Example 3

The headmaster of a certain school bought 49132 to be distributed to his 478 students. Estimate the number of books each student will get.


Make the equation first:-

This is simple word problem discussed in numbers, Here in order to obtain the real number of books each student will get you have to divide 49132 by 478, so the equation is 49132 ÷ 478 now approximate each number first:-


49132 to nearest ten thousands is 50,000 and 478 to nearest hundreds is 500 so the approximated equation will be 50,000 ÷ 500 = 100.

Therefore the estimated number of books each student will get is 100

  **************END OF TOPIC "Approximations" **************


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Category: Lower Secondary | Added by: Admin (27/Aug/2013) | Author: Yahyou M. Yahya E
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