JSS1 Second Term Mathematics Lesson Note – Approximation II

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WEEK 3

TOPIC: APPROXIMATION

CONTENTS

• Rounding off numbers to the nearest whole numbers, 10, 100, 1000, 0.5, 0.1, etc.
• Application of approximation in everyday life.
• Quantitative reasoning.

Rounding off numbers to nearest 10, 100 and 1 000

You recall that powers of ten as 10¹, 10²,10³ are 10, 100, 1 000 etc. respectively. When rounding off to any of these powers of ten, numbers half or above half of 10 are rounded off by adding one to the required digit, while the remaining lower digits are dropped   to zero.

Example 1

Round off 253 718 to the nearest thousand.

Solution

The thousand digits is 3, and the digit before it is 7.

Since 7 is higher than 5, hence it is rounded up to 10 and 1 is added to 3 to become 4, and the remaining digits are replaced with zero. That is;

253 718=254 000 to the nearest 1 000.This is because 718 is nearer to 1 000 than to 418  or 7 is nearer to 10 than it is to zero. This is known as rounding up.

Example 2

Round off 25 467 to nearest ten, and state the type of rounding off.

Solution

The ten digit is 6, and the digit before it is 7. As 7 is higher than 5, 1 is added to 6 to become 7.

25 467 = 25 470 this type is rounding up.

Example 3

Round off 46 960 to the nearest hundred.

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