Page 113 - Mathematics Coursebook

7.1 Simplifying fractions
11 Percentages

Percentages are everywhere. Key words
You will see percentages being used if you read a newspaper or Make sure you learn and
watch the news on television. Percentages are used to describe price understand these key words:
rises, how well you!ve done in a test, the chance of bad weather, per cent
product sales, and many other things.
percentage
fraction
quantity

"ere are two particular ways in which you can use percentages.

First, you can use them to compare di#erent things. Suppose you score 14 out of 20 in one test and 60
out of 75 in another one. Which was the better score? It is hard to say because they are marked out of
di#erent totals. However, if you change the marks to percentages they become 14 = 70%

20
and 60 = 80%. You can see immediately that the second mark was better.
75
Second, you can use percentages to describe increases or decreases. Suppose two items cost 20 dollars
and 40 dollars. If both prices are reduced by 10%, one will decrease by 2 dollars and the other by 4

dollars. "e percentage decrease is the same in both cases but the actual decrease is di#erent.
In this unit you will learn how to calculate and $nd percentages of amounts and use them to

make comparisons.

112 11 Percentages