NCERT Solutions Class 7 Mathematics Comparing Quantities Ex 8.2

Class 6 - Mathematics
Chapter - Comparing Quantities : Exercise 8.2

NCERT Solutions Class 7 Mathematics textbook
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Question: 1.Convert the given fractional numbers to percent:

(a) 1⁄8

(b) 5⁄4

(c) 3⁄40

(d) 2⁄7

Answer :
(a) 1⁄8 = 1⁄8 × 100% =25⁄2% = 12.5%

(b) 5⁄4 = 5⁄4 × 100% = 5 x 25% = 125%

(c) 3⁄40 = 3⁄40 × 100% = 3⁄2 × 5% = 15⁄2% = 7.5%

(d) 2⁄7 = 2⁄7 × 100% = 200⁄7% = 284⁄7%

Question: 2.Convert the given decimal fractions to percents:

(a) 0.65

(b) 2.1

(c) 0.02

(d) 12.35

Answer :
(a) 0.65 = 65⁄100 x 100% = 65%

(b) 2.1 = 210⁄100 x 100% = 210%

(c) 0.02 = 2⁄100 x 100% = 2%

(d) 12.35 = 1235⁄100 x 100% = 1235%

Question: 3.Estimate what part of the figures is coloured and hence find the percent which is coloured:

NCERT Solutions Class 7 Mathematics Comparing Quantities

Answer :
(i) Coloured part = 1⁄4

NCERT Solutions Class 7 Mathematics Comparing Quantities
Mddle block 1
∴ Percent of coloured part = 1⁄4 × 100% = 25%

(ii) Coloured part = 3⁄5

NCERT Solutions Class 7 Mathematics Comparing Quantities
∴ Percent of coloured part = 3⁄5 × 100% = 60%

(iii) Coloured part = 3⁄8

NCERT Solutions Class 7 Mathematics Comparing Quantities
∴ Percent of coloured part = 3⁄8 × 100% = 3⁄2×25%

= 37.5%

Question: 4.Find:

(a) 15% of 250

(b) 1% of 1 hour

(c) 20% of Rs. 2500

(d) 75% of 1 kg

Answer :
(a) 15% of 250 = 15⁄100 × 250 = 15 x 2.5 = 37.5

(b) 1% of 1 hours = 1% of 60 minutes = 1% of (60 x 60) seconds

= 1100×60×60 = 6 x 6 = 36 seconds

(c) 20% of Rs. 2500 = 20⁄100 × 2500 = 20 x 25 = Rs. 500

(d) 75% of 1 kg = 75% of 1000 g = 75⁄100 × 1000 = 750 g = 0.750 kg

Question: 5.Find the whole quantity if:

(a) 5% of it is 600

(b) 12% of it is Rs. 1080

(c) 40% of it is 500 km

(d) 70% of it is 14 minutes

(e) 8% of it is 40 liters

Answer :
Let the whole quantity be x in given Questions:

(a) 5% of x = 600 ⇒ 5⁄100 x x=600

⇒ x = 600 x 100⁄5 = 12,000

(b) 12% of x = Rs. 1080 ⇒ 12⁄100 x x=1080

⇒ x = 1080 x 100⁄12 = Rs. 9,000

(c) 40% of x = 500 km ⇒ 40⁄100 x x=500

⇒ x = 500 x 100⁄40 = 1,250 km

(d) 70% of x = 14 minutes ⇒ 70⁄100 x x=14

⇒ x = 14 x 100⁄40 = 20 minutes

(e) 8% of x = 40 liters ⇒ 8⁄100 x x = 40

⇒ x = 40 x 100⁄8 = 500 liters

Question: 6.Convert given percents to decimal fractions and also to fractions in simplest forms:

(a) 25%

(b) 150%

(c) 20%

(d) 5%

Answer :

S. No. Percents Fractions Simplest form Decimal form
(a) 25% 25⁄100 1⁄4 0.25
(b) 150% 150⁄100 3⁄2 1.5
(c) 20% 20⁄100 1⁄5 0.2
(d) 5% 5⁄100 1⁄20 0.05

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

Answer :
Given: Percentage of females = 30%

Percentage of males = 40%

Total percentage of females and males = 30 + 40 = 70%

Percentage of children = Total percentage – Percentage of males and females

= 100% – 70%

= 30%

Hence, 30% are children.

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 voters = 15,000

Percentage of voted candidates = 60%

Percentage of not voted candidates = 100 – 60 = 40%

Actual candidates, who did not vote = 40% of 15000

= 40100×15000 = 6,000

Hence, 6,000 candidates did not vote.

Question: 9.Meeta saves Rs. 400 from her salary. If this is 10% of her salary. What is her salary?

Answer :
Let Meera’s salary be Rs.x.

Now, 10% of salary = Rs. 400

⇒ 10% of x = Rs. 400

⇒ 10⁄100 x x = 400

⇒ x = 400 x 100⁄10

⇒ x = 4,000

Hence, Meera’s salary is Rs. 4,000.

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

Answer :
Number of matches played by cricket team = 20

Percentage of won matches = 25%

Total matches won by them = 25% of 20

= 25⁄100 x 20

= 5

Hence, they won 5 matches.

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