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(b) Let x be the percentage of the monthly rental spent to
the monthly salary of Ben.
Chemists use
x 450 proportions to calculate
=
100 3 750 the amount of each
pigment required to
450
x = × 100 produce the appropriate
3 750 colour of paint.
= 12
Ben spends 12% of his monthly salary on rental.

CHAPTER
4 Let y be the percentage of the monthly rental spent to the monthly salary of Farid.
y 550
=
100 5 000
550
y = × 100
5 000
= 11

Farid spends 11% of his monthly salary on rental.

Self Practice 4.5c

1. There are 40 passengers on a bus. At the next bus stop, 8 passengers get off and 18
passengers get on the bus.
(a) By applying the concept of proportions, determine the percentage of the
passengers who get off the bus compared to the number of passengers originally
on the bus.
(b) What is the ratio of the passengers who get on the bus at the bus stop compared
to the new total number of passengers on the bus?

4.5 Open the folder downloaded from page vii for extra
questions of Mastery Q 4.5.

1. In a basket, the ratio of the number of red apples to the number of green apples is
3 : 5.
(a) Write the fraction of the number of red apples over the total number of apples.
Hence, express this fraction in decimal.
(b) What is the percentage of red apples in the basket?

98
Chapter 4

04 TB Math F1.indd 98 11/10/16 12:12 PM