Lesson 8- Rounding Decimals

Objective

At the end of this lesson, students should be able round decimal numbers to the nearest whole number, tenth, hundredth or thousandth.

Rounding a decimal means representing it by a number to which the decimal is nearest to.

Rounding a decimal numbers allows us to write the number in a way to suit our purposes. Decimals can be rounded to the nearest whole number, tenth, hundredth, thousandth, etc.

If we are to round to the nearest whole number:

a) 3.54 = 4                b) 3.49 = 3                c) 3.504 = 4              d) 3.497 = 3

A similar idea is what we use to round figures. Below are some examples:

Example 1

Round these decimal numbers to the nearest whole number.

a) 2.63                       b) 13.429                 c) 238.532

Example 2

Round to the nearest tenth (1 decimal place):

a) 4.829                    b) 13.499                 c) 6.952

Example 3

Round to the nearest hundredth (2 decimal places)

a) 4.826                                b) 267.199                           c) 10.841

Example 4

Round to the nearest thousandth (3d.p)

a) 2.8469                              b) 18.2195                           c) 9.1111

Solution

a) 2.8469 = 2.847

b) 18.2195 = 18.220

c) 9.1111 = 9.111