Page 284 - Math Smart - 7

12.2.2 Express one quantity as a

percentage of another

To express Quantity A as percentage of Quantity B, write Quantity A as a fraction
of Quantity B. Then express the fraction as a percentage.

Example 6

28 of the 40 pupils in a class are boys. What percentage of the pupils are boys?

Solution
Number of boys in the class = 28.
Percentage of the pupils who are boys = N^^^befofpu^ ^ ""OOyo

7 10

1
= 7 X 10%
= 70%
70% of the pupils are boys.

Example 7

May has 54 stickers and ice has 90 stickers. Express the number of stickers May has
as a percentage of the number of stickers Ice has.
Solution
1^X100% = 60%

The number of stickers May has is 60% of the number of stickers Ice has.

Jim has a mass of 60 kg and Ong has a mass of 56 kg. Express Ong's mass as a
percentage of Jim's mass.
Solution
X 100% = 93^ %
To express a quantity as
a percentage of another
Ong's mass is 93i % of Jim's mass.
quantity, make sure that
they are expressed in the
same units.
Express 90 minutes as a percentage of 2 hours.
Solution
2 h = 120 min
90
X 100% = 75%
120
90 minutes is 75% of 2 hours.

Percentages