Chapter -8 Comparing Quantities | Class 7th |NCERT Maths Solutions | Edugrown

Ex 8.1 Class 7 Maths Question 1.
Find the ratio of:
(a) ₹5 to 50 paise
(b) 15 kg to 210 kg
(c) 9 m to 27 cm
(d) 30 days to 36 hours
Solution:

Ex 8.1 Class 7 Maths Question 2.
In a computer lab, there are 3 computers for every 6 students. How many computers are needed for 24 students?
Solution:
∵ For every 6 students, there are 3 computers
∴ For 1 student there are 36 computer
∴ For 24 students there are 36 × 24 computers = 12 computers
Hence, 12 computers are needed for 24 students.

Ex 8.1 Class 7 Maths Question 3.
Population of Rajasthan = 570 lakhs and population of U.P. = 1660lakhs. Area of Rajasthan = 3 lakh km2 and area of U.P. = 2 lakh km².
(i) How many people are there per km² in both these states?
(ii) Which state is less populated?
Solution:

Ex 8.2 Class 7 Maths Question 1.
Convert the given fractional number to per cents :
(a) 18
(b) 54
(c) 340
(d) 27
Solution:

Ex 8.2 Class 7 Maths Question 2.
Convert the given decimal fractions to per cents.
(a) 0.65
(b) 2.1
(c) 0.02
(d) 12.35
Solution:

Ex 8.2 Class 7 Maths Question 3.
Estimate what part of the figures is coloured and hence find the per cent which is coloured.

Solution:

Ex 8.2 Class 7 Maths Question 4.
Find :
(a) 15% of 250
(b) 1% of 1 hour
(c) 20% of ₹ 2500
(d) 75% of 1 kg
Solution:

Ex 8.2 Class 7 Maths Question 5.
Find the whole quantity if
(a) 5% of it is 600
(b) 12% of it is ? 1080
(c) 40% of it is 500 km
(d) 70% of it is 14 minutes
(e) 8% of it is 40 litres
Solution:

Ex 8.2 Class 7 Maths Question 6.
Convert given per cents to decimal fractions and also to fractions in simplest forms :
(a) 25%
(b) 150%
(c) 20%
(d) 5%
Solution:

Ex 8.2 Class 7 Maths Question 7.
In a city, 30% are females, 40% are males and remaining are children. What per cent are children?
Solution:
In a city,
Percentage of females = 30%
Percentage of males = 40%
Percentage of children = (100 – 30 – 40)% = 30%

Ex 8.2 Class 7 Maths Question 8.
Out of 15,000 voters in a constituency, 60% voted. Find the percentage of voters who did not vote. Can you now find how many actually did not vote?
Solution:
Percentage of voters who voted = 60%
Percentage of voters who did not vote = (100 – 60)% = 40%
Total number of voters = 15000
Number of voters who did not vote
= 40% of 15000
= ( 40100 × 15000 ) = 6000

Ex 8.2 Class 7 Maths Question 9.
Meeta saves ₹ 400 from her salary. If this is 10% of her salary, what is her salary?
Solution:

Ex 8.2 Class 7 Maths Question 10.
A local cricket team played 20 matches in one season. It won 25% of them. How many matches did they win?
Solution:
Out of 100, 25% matches are won. Then, out of 20, the number of matches that the team won
= 25100 × 20 = 14 × 20 = 5

Ex 8.3 Class 7 Maths 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:

Ex 8.3 Class 7 Maths 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:

Ex 8.3 Class 7 Maths 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 = ( 50025000 × 100 ) % = 2%

Ex 8.3 Class 7 Maths 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 = ( 20000350000 × 100 )% = 407 % = 5 57%

Ex 8.3 Class 7 Maths 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:

Ex 8.3 Class 7 Maths 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%.

Ex 8.3 Class 7 Maths 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:

Ex 8.3 Class 7 Maths Question 8.
Amina buys a book for ₹ 275 and sells it at a loss of 15%. How much does she sell it for?
Solution:

Ex 8.3 Class 7 Maths 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:

Ex 8.3 Class 7 Maths Question 10.
What rate gives ₹ 280 as interest on a sum of ₹ 56,000 in 2 years?
Solution:

Ex 8.3 Class 7 Maths 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: