# Lesson 11- Estimation Of Decimals

Objective

At the end of this lesson, students should be able to estimate the answers to questions involving addition and subtraction of decimals.

An estimate is a rough guess. In this lesson, we will learn how to estimate decimals in addition and subtraction questions.

To estimate a decimal, you may quickly round it to the nearest whole number, tenth, hundredth or thousandth before adding or subtracting.

Example 1

Estimate the following decimals.

a) 4.6 + 2.1      b.  5.1 – 3.5 Example 2 Example 3

Estimate to the nearest hundredth.

a) 13.725 + 3.123      b.  15.123 – 12.281

Solution

NB: The decimals are rounded to 2 decimal places before adding or subtracting. Unit 10 Lesson 11: Exercise 1 1) 21   2) 6   3) 70   4) 66   5) 32
6) 5   7) 9   8) 28   9) 50   10) 5

Unit 10 Lesson 11: Exercise 2 1) 9.0   2) 6.9   3) 2.0   4) 10.4   5) 5.8
6) 34.5   7) 34.9   8) 41.1   9) 16.5   10) 3247.5

Unit 10 Lesson 11: Exercise 3

Estimate these decimals. Your answers should be left at 2 decimal places. 1) 770.51   2) 6.38   3) 33.81   4) 133.88   5) 53.83
6) 70.32   7) 10.18   8) 7.14   9) 4.50   10) 11.56

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