NCERT Book Class 8 Maths Chapter 7 Comparing Quantities

COMPARING QUANTITIES 79

CHAPTER

Comparing Quantities
7
7.1 Recalling Ratios and Percentages
We know, ratio means comparing two quantities.
A basket has two types of fruits, say, 20 apples and 5 oranges.
Then, the ratio of the number of oranges to the number of apples = 5 : 20.
5 1
The comparison can be done by using fractions as, =
20 4
1
The number of oranges is th the number of apples. In terms of ratio, this is
4
1 : 4, read as, “1 is to 4”
OR
20 4
Number of apples to number of oranges = = which means, the number of apples
5 1
is 4 times the number of oranges. This comparison can also be done using percentages.

There are 5 oranges out of 25 fruits. By unitary method:
So percentage of oranges is Out of 25 fruits, number of oranges are 5.
5 4 20 So out of 100 fruits, number of oranges
× =
= 20% OR
25 4 100 5
= × 100 = 20.
[Denominator made 100]. 25

Since contains only apples and oranges,
So, percentage of apples + percentage of oranges = 100
or percentage of apples + 20 = 100
or percentage of apples = 100 – 20 = 80
Thus the basket has 20% oranges and 80% apples.
Example 1: A picnic is being planned in a school for Class VII. Girls are 60% of the
total number of students and are 18 in number.
The picnic site is 55 km from the school and the transport company is charging at the rate
of ` 12 per km. The total cost of refreshments will be ` 4280.