Page 101 - ICSE Math 8

\ 10 men and 5 women = 14 women + 5 women = 19 women
Let ` x be the earning by 5 women and 10 men in one day.

\ ` x will also be the earning of 19 women in one day.
Note that more the number of women, more will be the earning. So, number of women is in
direct variation with the earnings.

7 875
\ = (cross-multiply)
19 x Using unitary method:
fi 7x = 875 × 19 7 women earn ` 875 in a day.
875 19× 1 woman earn ` 875 in a day.
fi x = = 2,375 7
7 875
Hence, 5 women and 10 men earn ` 2,375 19 women will earn ` 7 × 19 = ` 2,375
in one day. in a day.

EXERCISE 9.1

1. Which of the following show direct variation?
(a) Height of a child (x) and his weight (y) as he grows
(b) Distance travelled (x) and time taken (y), if a car is not moving at a uniform speed
(c) Wages of a worker (x) and the number of hours of work (y)

(d) The number of students (x) and the fees paid by them (y)
(e) Number of rainy days (x) and the amount of rainfall on those days (y)
2. Complete the following tables assuming that x is in direct variation with y.

(a) x 60 ... 180 ... ... ... (b) x ... 9 ... 15 ... 26.5

y 4 8 12 15 20 25 y 3.5 4.5 6.5 ... 9.25 ...

3. Vicky bought 15 notebooks for ` 240. How many notebooks can he buy for ` 160?
4. Arushi takes 130 minutes to walk a distance of 110 metres. How much time will she take to walk a
distance of 275 metres?
5. A train is moving at an average speed of 70 km/h. How much distance will it cover in 25 minutes?
6. On a particular day, 150 US dollars are worth ` 7,425. On the same day, what will be the worth of 250
US dollars?
7. If 5 men or 8 women earn ` 625 per day, how much would 8 men and 12 women earn per day?
8. A worker is paid ` 2400 for 5 days work. If his total income is ` 10,080, for how many days did he
work?
9. The amount of extension in an elastic string is in direct variation with the weight hung on it. If a
weight of 250 g produces an extension of 3.5 cm, then what weight would produce an extension of
21 cm?
10. The thickness of 12 sheets of chart papers is 35 mm. What is the thickness of 294 sheets of chart
papers?
8
11. In 12 days, the earth picks up 1.8 × 10 kg of dust from the atmosphere. In how many days will it pick
8
up 7.2 × 10 kg of dust?
2
2
12. 35 children need 122.5 m of space for a dance performance. If the available space is 21 m , how many
children can give the performance?

89