Definition of estimation

It is the approximate calculation of a value or quantity. Estimation is usually done by using methods of approximation.

Methods of approximation

This method involves rounding up or rounding down a number to the nearest whole number. If the digit considered is less than 5, round down but if the digit is equal or greater than 5, round up.

Ex: round up or round down the following to the nearest ten.

a)235.702, b)672.798

Solution: a) 235.702 to the nearest ten = 235 = 240

b) 672.798 to the nearest ten = 672 = 673

Decimal places (d.p)

Convert each of the following correct to their required number of decimal places;

a) 34.1426 to 2d.p and 3d.p, b) 0.0082367 to 1d.p

Solution: a) 34.14 to 2d.p and 34.143 to 3d.p     b)0.008 to 1d.p

Significant figures (s.f)

The first digit on the left of a number different from zero is called significant figure.

Ex: convert 5.200458 correct to 1s.f, 2s.f, 5s.f and 6s.f   

Solution: 5 to 1s.f, 5.2 to 2s.f, 5.20 to 3s.f, 5.2005 to 5s.f, 5.20046 to 6s.f