Class 7 Maths NCERT Solutions for Chapter – 8 Comparing Quantities Ex – 8.3

Comparing Quantities

Question 1.
Tell what is the profit or loss in the following transactions. Also find profit per cent or loss per cent in each case.
(a) Gardening shears bought for ₹ 250 and sold for ₹ 325.
(b) A refrigerator bought for ₹ 12,000 and sold at ₹ 13,500.
(c) A cupboard bought for ₹ 2,500 and sold at ₹ 3,000.
(d) A skirt bought for ₹ 250 and sold at ₹ 150.

Solution:

Question 2.
Convert each part of the ratio to percentage :
(a) 3 : 1
(b) 2 : 3 : 5
(c) 1 : 4
(d) 1 : 2 : 5

Solution:

Question 3.
The population of a city decreased from 25,000 to 24,500. Find the percentage decrease.

Solution:
Original population of the city = 25000
Decreased population of the city = 24500
∴ Decrease in population = 25000 – 24500 = 500
∴ Percentage of decrease = (  × 100 ) % = 2%

Question 4.
Arun bought a car for ₹ 3,50,000. The next year, the price went upto ₹ 3,70,000. What was the percentage of price increase?

Solution:
Original cost of the car = ₹ 3,50,000
Increased cost of the car = ₹ 3,70,000
∴ Increase in price = ₹ (370000 – 350000)
= ₹ 20,000
∴ Percentage increase = (  × 100 )% =  % = 5 %

Question 5.
I buy a T.V. for ₹ 10,000 and sell it at a profit of 20%. How much money do I get for it?

Solution:

Question 6.
Juhi sells a washing machine for ? 13,500. She loses 20% in the bargain. What was the price at which she bought it?

Solution:
We have, S.P. = ₹13,500 and loss = 20%.

Question 7.
(i) Chalk contains calcium, carbon and oxygen in the ratio 10:3:12. Find the percentage of carbon in chalk.
(ii) If in a stick of chalk, carbon in 3g, what is the weight of the chalk stick?

Solution:

Question 8.
Amina buys a book for ₹ 275 and sells it at a loss of 15%. How much does she sell it for?

Solution:

Question 9.
Find the amount to be paid at the end of 3 years in each case :
(a) Principal = ₹ 1,200 at 12% p.a.
(b) Principal = ₹ 7,500 at 5% p.a.

Solution:

Question 10.
What rate gives ₹ 280 as interest on a sum of ₹ 56,000 in 2 years?

Solution:

Question 11.
If Meena gives an interest of ₹ 45 for one year at 9% rate p.a. What is the sum she has borrowed?

Solution: