Page 73 - Mathematics

Example 4.10 7 x
Writing in fraction gives, =
The first, second, third, and fourth terms 12 1380
are proportional. If the first, second, Cross multiplication gives,
and third terms are 42, 36, and 35, 12x = 7 1380×
respectively, find the fourth term. 7 1380× Tanzania Institute of Education
x =
Solution 12
Let x be the fourth term. 805.=
Thus, 42, 36, 35, x are in proportion. Therefore, the number of girls is 805.
Writing the numbers in ratios gives, (b) The total number of students
42 = 35 = number of girls + number of boys

36 x = 805 + 1380
Cross multiplication gives, = 2,185.
42 x×= 35 36× Therefore, the total number of students
35 36× in the school is 2,185.
x =
42
= 30. Example 4.12
Therefore, the fourth term is 30.
In a road safety campaign, it was revealed
that 1 out of every 10 drivers in a certain
Example 4.11 city attended safety driving seminars. If
there were 400 drivers in the city, how
The ratio of the number of girls to that of many drivers have attended the seminars?
boys in a school is 7:12. If the number Solution
of boys is 1,l380, find: Let y be the number of drivers who are
(a) the number of girls. likely to have attended driving seminars.
(b) the total number of students in the Given
school. The ratio of drivers who have attended

Solution safety driving seminars 1:10=
(a) Given The ratio of the drivers who are likely
Number of girls: number of boys =7:12 to have attended the seminar = y : 400
Number of boys = 1,380 According to proportions, the two ratios
Let x be the number of girls. It follows are equal. Thus, Mathematics Form One
that 7:12 = x :1380. 1 = y
10 400

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25/10/2024 09:51:20
Mathematics form 1.indd 67
Mathematics form 1.indd 67 25/10/2024 09:51:20