Exercise 3.4

Exercise 3.4

1. Fill in the blanks.

(i) If the cost of 3 pens is ₹ 18, then the cost of 5 pens is __________. Answer: ₹.30

(ii) If Karkuzhali earns ₹ 1800 in 15 days, then she earns ₹ 3000 in __________days. Answer: 25

2. Say True or False.

(i) If the weight of 40 books is 8 kg, then the weight of 15 books is 3kg. [True]

(ii) A car travels 90 km in 3 hours with constant speed. It will travel 140 km in 5 hours at the same speed. [False]

3. If a person reads 20 pages of a book in 2 hours, how many pages will he read in 8 hours at the same speed?

Solution:

2 hours reading no. of pages = 20

In 1 hour, reading = 20/2

In 8 hours reading = 20/2 × 8 = 80

In 8 hours he read = 80 pages

4. The cost of 15 chairs is ₹ 7500. Find the number of such chairs that can be purchased for ₹ 12,000?

Solution:

The cost of 15 chairs = ₹.7500

Fractional form = 15/7500

For Rs. 12,000 no. of chairs = 15/7500 × 12000

= 120/5 = 24

For ₹. 12,000 no. of chairs = 24 chairs.

5. A car covers a distance of 125 km in 5 kg of LP Gas. How much distance will it cover in 3 kg of LP Gas?

Solution:

A car covers 125 km by using gas of = 5 kg

For 1 kg gas = 125/5

For 3 kg gas = 125/5 × 3

= 75 km

The distance covers for 3 kg gas = 75 km

6. Cholan walks 6 km in 1 hour at constant speed. Find the distance covered by him in 20 minutes at the same speed.

Solution: Cholan walks 6 km in 1 hour = 60 minutes

for 1 minute = 6/60

for 20 minute = 6/60  × 20

for 20 minutes he walk = 2 km

7. The number of correct answers given by Kaarmugilan and Kavitha in a quiz competition are in the ratio 10 : 11. If they had scored a total of 84 points in the competition, then how many points did Kavitha get?

Solution:

Kaarmugilan : Kavitha = 10 : 11

Total score = 84 points

Total parts = 10 + 11

= 21

For 1 part = 84/21  = 4 points

Kavitha Score = 11 parts

11 parts = 11 × 4

= 44 points

Kavitha Scored = 44 points.

8. Karmegan made 54 runs in 9 overs and Asif made 77 runs in 11 overs. Whose run rate is better? (run rate = ratio of runs to overs)

Solution:

Karmegan run rate = 54 : 9

For one over = 54/9 = 6

Asif run rate = 77 : 11

For one over = 77/11 = 7  i.e., 7 > 6

Asif run rate is better than Karmegan.

9. You purchase 6 apples for ₹ 90 and your friend purchases 5 apples for ₹ 70. Whose purchase is better?

Solution:

My purchase 6 apples = Rs.90

Friend purchase 5 apples = Rs.70

One apple cost = 90/6 & 70/5

= 15 > 12

My friend’s rate of purchase is better than me.

Objective Type Questions

10. If a barbie doll costs ₹ 90, then the cost of 3 such dolls is ₹ ___________.

(a) 260

(b) 270

(c) 30

(d) 93

Answer: (b) 270

11. If 8 oranges cost ₹ 56, then the cost of 5 oranges is ₹ ___________.

(a) 42

(b) 48

(c) 35

(d) 24

Answer: (c) 35

12. If a man walks 2 km in 15 minutes, then he will walk ___________ km in 45 minutes.

(a) 10

(b) 8

(c) 6

(d) 12

Answer: (c) 6 

Answers:

Exercise 3.4

1) (i) Rs.30 (ii) 25 days

2) (i) True (ii) False

3) 80 Pages

4) 24 Chairs

5) 75km

6) 2 km

7) 44 points

8) Asif’s run rate is better

9) My friend’s rate of purchase is better than me.

10) (b) 270

11) (c) 35

12) (c) 6 km