NCERT Class 7 Maths Chapter 8 Comparing Quantities Exercise 8.2

Chapter 8 Comparing Quantities Exercise 8.2

Question 1: Convert the given fractional numbers to percent.
(a) 1/8

Answer:
1/8  x 100 = 100/8 = 12.5%

(b) 5/4
Answer:

5/4  x 100 = 500/4 = 125%

(c) 3/40
Answer:

3/40  x 100 = 300/40 = 7.5%

(d) 2/7
Answer:

2/7  x 100 = 200/7 = 28 4/7%

Question 2: Convert the given decimal fraction to percent.
(a) 0.65
Answer:

65/100  x 100 = 6500/100 = 65%

(b) 2.1
Answer:

21/10  x 100 = 2100/10 = 210%

(c) 0.02
Answer:

2/100  x 100 = 200/100 = 2%
 (d) 12.35
Answer:
1235/100  x 100 = 123500/100 = 1235%

Question 3: Estimate what part of the figures is coloured and hence find the per cent which is coloured.
(i)

Answer:
The shaded part is  1/4.
1/4  x 100 = 100/4 = 25%.

(ii)

Answer:
The shaded part is  3/5.
3/5  x 100 = 300/5 = 60%.

(iii)

Answer:
The shaded part is  3/8.
3/8  x 100 = 300/8 = 37.5%.

Question 4: Find:
(a) 15% of 250
Answer:

15/100  x 250 = 3750/100 = 37.5

(b) 1% of 1 hour
Answer:

1/100  x 1 = 1/100 = 0.01 hour

(c) 20% of ₹ 2500
Answer:

20/100  x 2500 = 50000/100 = ₹500

(d) 75% of 1 kg
Answer:
75/100  x 1000 = 75000/100 = 750 grams

Question 5: Find the whole quantity if
(a) 5% of it is 600
Answer:

= 5% of __ = 600
= 5/100  x x=600 = 1x/20=600
= x =  (600 x 20)/1 = 12000

(b) 12% of it is ₹ 1080.
Answer:

= 12% of __ = ₹ 1080
= 12/100  x x=₹ 1080 = 3x/25=₹1080
= x =  (1080 x 25)/3 = 27000/3 = ₹ 9000

(c) 40% of it is 500 km
Answer:
= 40% of __ = 500 km
= 40/100  x x=500 km = 2x/5= 500 km
= x =  (500 x 5)/2 = 2500/2 = 1250 km

(d) 70% of it is 14 minutes
Answer:

= 70% of __ = 14 minutes
= 70/100  x x=14 minutes = 7x/10= 14 minutes
= x =  (14 x 10)/7 = 140/7 = 20 minutes

(e) 8% of it is 40 liters
Answer:

= 8% of __ = 40 liters    
= 8/100  x x=40 liters = 2x/25= 40 liters
= x =  (40 x 25)/2 = 1000/2 = 500 liters

Question 6: Convert given percent to decimal fractions and also fractions in simplest forms:
(a) 25%
Answer:

= 25% = 25/100  = 1/4

(b) 150%
Answer:

= 150% = 150/100  = 3/2

(c) 20%
Answer:

= 20% = 20/100  = 1/5

(d) 5%
Answer:

= 5% = 5/100  = 1/20

Question 7: In a city, 30% are females, 40% are males and remaining are children. What per cent are children?
Answer:

Percentage of female in the city = 30%
Percentage of male in the city = 40%
Percentage of children in the city = ?

= 100% - (30% + 40%)
= 100% - 70%
= 30%
Therefore, the percentage of the children in the city is 30%.

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?
Answer:

Total number of voters = 15000
Percentage of voters who voted = 60%
Percentage of voters who didn’t vote = ?

= 100% - 60%
= 40%
Therefore, out of 15000 voters, 40% of the voters didn’t vote.
Number of the voters who didn’t vote = ?
= 40/100 x 15000 600000/100 = 6000

Therefore, 6000 voters didn’t vote.

Question 9: Meeta saves ₹ 4000 from her salary. If this is 10% of her salary. What is her salary?
Answer:

Amount Meeta saves from her salary = ₹ 400
= 10% of her salary
(Let her salary be x)
= 10% of x = ₹ 400
= 10/100  x x=400
= 1x/10  =400
= x = (400 x 10)/1 = ₹ 4000

Therefore, Meeta’s salary is ₹ 4000.

Question 10: A local cricket team played 20 matches in one season. It won 25% of them. How many matches did they win?
Answer:

Total matches played = 20
Percentage of matches won = 25%

Therefore, number of matches won = 25% of 20
= 25/100  x 20 = 500/100 = 5

Therefore, they won 5 matches.

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