Ncert Solutions For Class 7 Maths Ex 8.2

Ncert Solutions For Class 7 Maths Chapter 8 Ex 8.2

QUESTION 1:

Convert the given fractional numbers to percent:

(a) 1/3                       (b)6/5                        (c)4/25                      (d)3/7

Solution;

(a) 1/3 = (1/3) x 100% = 100/3 = 33.33%

(b) 6/5 = (6/5) x 100%  = 6 x 20 = 120%

(c)  4/25 = (4/25) x 100% = 16%

(d) 2/7 = (2/7) x 100% = 28.57%

 

QUESTION 2:

Express the given decimal numbers in percentages.

(a) 0.31         (b)0.03                      (c)19.62        (d)0.007

Solutions;

(a) 0.31 = (31/100) x 100% = 31%

(b) 0.03 = (3/100) x 100%   = 3%

(c) 19.62 = (1962/100) x 100% = 1962%

(d) 0.007 = (7/1000) x 100% = 0.7%

 

 QUESTION 3:

Find what part of the following figures is colored; also find the percentage of the colored part.

Comparing

Solutions;

(i) Colored part = 1/4

Therefore, percentage of the colored portion = (1/4) x 100%  = 25%

(ii) Colored portion = 3/5

Therefore, percentage of the colored portion = (3/5) x 100 =60%

(iii) Colored portion = (3/8) x 100% = 37.5%

 

QUESTION 4:

Calculate :

(a) 15% of 450                    (b) 2% of 2 hour

 (c) 10% of ₹2600              (d) 50% of 5 kg

Solutions;

(a) 15% of 450 = (15/100) x 450 = 67.5

(b) 2% of 2 hours= 2% of (2×3600) secs         (Since 1 hour = 60 x 60 secs)

= (2/100) x 7200 =144secs.

(c) 10% of Rs.2600 = (10/100) x 2600

=Rs.260

(d) 50% of 5kg         = 50% of (5000g)              (Since 1kg = 1000g)

= (50/100) x 5000

= 2500 g or 2.5kg

 

 QUESTION 5:

Calculate the total quantity if:

 (a) 5% of it is 100             

(b) 10% of it is ₹1060

(c) 20% of it is 800 km

(d) 90% of it is 18 minutes

(e) 9% of it is 60 liters

Solutions;

let the total quantity be Y in all above cases,

(a)5% of Y  = 100

=> (5/100) x Y =100

=> Y=(100×100)/5 =2000

(b)10% of Y = 1060

=> (10/100) x Y = 1060

=> Y = (1060 x 100)/10 = Rs.10600

(c)20% of Y = 800

=> (20/100) x Y = 800

=> Y = (800 x 100)/20 = 4000km

(d) 90% of Y = 18min

=> (90/100) x Y = 18

=> Y=(18 x 100)/90 =20mins.

(e) 9% of Y = 60

=> (9/100) x Y = 60

=> Y = (60 x 100)/9 =666.66liters.

 

QUESTION 6:

Convert the following percentages to fractions , simplest fractions and decimal numbers:

(a)20%                      (b)25%                      (c)5%             (d)120%

Solution;

Percentage Fractions Simplest Fraction Decimal Numbers.
20% 20/100 1/5 0.2
25% 25/100 1/4 0.25
5% 5/100 1/20 0.05
120% 120/100 6/5 1.2

 

QUESTION 7:

12000 voters constituted a constituency, out of which 80% voted. What percentage and number of voters did not vote?

Solution;

Given,

Total no. of voters = 12000

Percentage who voted = 80%

Thus, percentage who did not vote = 100 -80 = 20%

Therefore, the number of people who did not vote = 20% of 12000

= (20/100) x 12000 = 2400

 

QUESTION 8:

Sanjay saves Rs.5000 every month, if this is 20% of his salary. What is his monthly salary?

Solution;

Let Sanjay’s salary be Y

Now, 20% of Y = 5000

(20/100) x Y = 5000

Y = Rs.25000

Therefore,Sanjay’s salary is Rs.25000

 

QUESTION 9:

A localdota team played 10 matches in a season. If they won 40% of their matches, in how many matches do they win?

Solution;

Given,

Number of matches played by the dota2 team =10

Percentage of matches won = 40%

Therefore, total matches they were victorious in = 40% of 10

= (40/100) x 10

=4.

 

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