year 8 maths

236 Chapter 4 Fractions, decimals, percentages and financial mathematics
4G Finding a percentage and expressing as a percentage
Showing values in percentages ‘standardises’ the value and makes it easier for comparisons to be made.
For example, Huen’s report card could be written as marks out of each total or in percentages:
French test 14
20
German test 54
75
French test 70%
German test 72%
It is clear that Huen’s German score was the stronger result. Comparison is easier when proportions
or fractions are written as percentages (equivalent fractions with denominator of 100 ). Expressing one
number as a percentage of another number is the technique covered in this section.
Another common application of percentages is to find a certain percentage of a given quantity.
Throughout your life you will come across many examples in which you need to calculate percentages
of a quantity. Examples include retail discounts, interest rates, personal improvements, salary increases,
commission rates and more.
L et’s start: What percentage has passed?
Answer the following questions.
• What percentage of your day has passed?
• What percentage of the current month has passed?
• What percentage of the current season has passed?
• What percentage of your school year has passed?
• What percentage of your school education has passed?
• If you live to an average age, what percentage of your life has passed?
• When you turned 5 , what percentage of your life was 1 year?
• When you are 40 , what percentage of your life will 1 year be?
Cambridge Maths NSW
Stage 4 Year 8 Second edition
ISBN 978-1-108-46627-1 © Palmer et al. 2018
Cambridge University Press
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