Haryana State Board HBSE 7th Class Maths Solutions Chapter 8 Comparing Quantities Ex 8.3 Textbook Exercise Questions and Answers.

## Haryana Board 7th Class Maths Solutions Chapter 8 Comparing Quantities Exercise 8.3

Question 1.

Tell what is the profit or loss in the following transction. Also find profit % or loss % in each case.

(a) Gardening shears bought for Rs. 250 and sold for Rs. 325.

(b) A fridge bought for Rs. 12,000 arid sold at Rs. 13,500.

(c) A cupboard bought for Rs. 2500 and sold at Rs. 3000.

(d) A skirt bought for Rs. 250 and sold at Rs. 150.

Solution:

(a) C.P. = Rs. 250

S.P. = Rs. 325

Profit or gain = S.P. – C.P.

= 325 – 250 = Rs. 75

Gain % = \(\frac{\text { Gain }}{\text { C.P. }}\) x 100

= \(\frac{75}{250}\) x 100

∴ gain % = 30%

C.P. = Rs. 12,000,

S.P. = Rs. 13,500

Profit = 13,500-12,000

= Rs. 1,500

Profit % = \(\frac{1500}{12000}\) x 100 = 12\(\frac{1}{2}\)%

(c) C.P. = Rs. 2500 S.P. = Rs. 3000

Profit = 3000 – 2500 = Rs. 500

Profit % = \(\frac{500}{2500}\) x 100 = 20%

(d) C.P. = Rs. 250 S.P. = Rs. 150

Loss = C.P. – S.P.

= 250 – 150 = Rs. 100

Loss % = \(\frac{\text { Loss }}{\text { C.P. }}\) x 100

= \(\frac{100}{250}\) x 100 = 40%

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:

(a) Total part of Ratio = 3 + 1 = 4

= \(\frac{3}{4}=\frac{3}{4}\) x 100% = 75%

= \(\frac{1}{4}=\frac{1}{4}\) x 100% = 25%

(b) Total part of Ratio = 2 + 3 + 5 = 10

(c) Total part of Ratio =1 + 4 = 5

(d) Total part of ratio = l + 2 + 5 = 8

Question 3.

The population of a city decreased from 25000 to 24500. Find the percent decrease.

Solution:

Percent decrease

∴ Percent decrease = 2%.

Question 4.

Arun bought a car for Rs. 3,50,000. The next year, the price went upto Rs. 3,70,000. What was the percent increase ?

Solution:

Percent increase

Question 5.

I buy a T.V. for Rs. 10,000 and sell it at a profit of 20%. What do I get for it ?

Solution:

C.P. = Rs. 10,000, S.P. = ?

Profit = 20%

∴ S.P. = Rs. 12000

Profit = S.P. – C.P.

= 12000 -10000

∴ Profit = Rs. 2000

Question 6.

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

S.P. = Rs. 13,500, loss = 20%,

C.P. = ?

or 8 C.P. = 13500 x 10

∴ C.P = \(\frac{135000}{8}\) = Rs. 16875.

Question 7.

(i) Chalk contains calcium, carbon and oxygen in the ratio 10 : 3 : 12. Find percent of carbon in chalk.

(ii) If in a stick of chalk, carbon is 3g, what is the weight of the chalk stick ?

Solution:

(i) Calcium : Carbon : Oxygen

= 10:3 : 12

Total part of Ratio = 10 + 3 + 12 = 25

Percent of calcium in chalk = \(\frac{10}{25}\) x 100% = 40%

Percent of carbon in chalk = \(\frac{3}{25}\) x 100% = 12%

Percent of oxygen in chalk = \(\frac{12}{25}\) x 100% = 48%

(ii) Let total weight of carbon = x

According to question, 12% of x = 3 gm

or, \(\frac{12}{100}\) x x = 3

x = \(\frac{3 x 100}{100}\) = 25

Hence total weight of carbon = 25 gm.

Question 8.

Amina buys a book for Rs. 275 and sells it at a loss of 15%. IIow much does she sell it for ?

Solution:

C.P. = Rs. 275, S.P. = ?

Loss = 15%

S.P = \(\left(\frac{100-\operatorname{Loss} \%}{100}\right)\) x 275 = Rs. 233.75

Question 9.

Find the amount to be paid at end of 3 years in each case :

(a) Principal = Rs. 1200 at 12% p.a.

(b) Principal = Rs. 7500 at 5%p.a.

Solution:

(a) S.I = \(\frac{\mathrm{PRT}}{100}\)

= \(\frac{1200 \times 12 \times 3}{100}\) = Rs. 432

A = P + I = 1200 + 432

= Rs. 1632

(b) S.I. = \(\frac{7500 \times 5 \times 3}{100}\) = Rs. 1125

A = P + I = 7500 + 1125

= Rs. 8625.

Question 10.

What is the rate of interest which gives an interest of Rs. 280 on a sum of Rs. 56000 for 2 years ?

Solution:

P =Rs. 56000,

S.I. = Rs. 280, T = 2 years,

R =?

.’. Rate of interest = 0.25%.

Question 11.

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

Solution:

S.I. = Rs. 45, R = 9%,

T = 1 year, P = ?

P = \(\frac{\text { S.I. } \times 100}{R \times T}=\frac{45 \times 100}{9 \times 1}\)

.’. Sum = Rs. 500.