## Ex 6.3 Class 7 ML Aggarwal

Question 1.

6 bowls cost ₹ 90. What would be the cost of 10 such bowls?

Solution:

Cost of 6 bowls = ₹ 90

Let cost of 10 bowls = ₹ x

6 : 10 = 90 : x

⇒ 6 × x = 10 × 90 (ad = bc)

x = ₹ 150

Cost of 10 bowls = ₹ 150

Question 2.

Ten pencils cost ₹ 15. How many pencils can be bought with ₹ 72?

Solution:

Cost of 10 pencils = ₹ 15

Let number of pencils will be bought in ₹ 72 = x

10 : x = 15 : 72

x × 15 = 10 × 72 (bc = ad)

x = 48

Number of pencils = 48

Question 3.

400 grams cake costs 80 rupees. How much would a 1.5 kg cake cost?

Solution:

Cost of 400 g cake = ₹ 80

Let cost of 1.5 kg cake = ₹ x

1.5 kg = 1500 gm

400 : 1500 = 80 : x

400 × x – 1500 × 80 (ad = bc)

x = ₹ 300

Cost of 1.5 kg = ₹ 300

Question 4.

A man earns ₹ 18000 in 3 months.

(i) How much time would he take to earn ₹ 30000?

(ii) How much money will he earn in 7 months?

Solution:

A man earns in 3 months = ₹ 18000

Let ₹ 30000 be earned in = x months

18000 : 30000 = 3 : x (ad = bc)

18000 × x = 30000 × 3

x = 5

₹ 30000 will be earn in 5 months

(ii) Let money will be earned in 7 months = ₹ x

3 : 7 = 18000 : x (ad = bc)

3 × x = 7 × 18000

x = 42000

A money of ₹ 42000 will be earned.

Question 5.

12 mangoes weigh 2.4 kg. What is the weight of 8 mangoes?

Solution:

Weight of 12 mangoes = 2.4 kg

Let weight of 8 mangoes = x kg

12 : 8 = 2.4 : x

12 × x = 8 × 2.4

x = 1.6

Weight of 8 mangoes = 1.6 kg

Question 6.

If the weight of 12 sheets of thick paper is 40 grams, how many sheets of the same paper would weigh 2\(\frac { 1 }{ 2 }\) kilograms?

Solution:

Weight of 12 sheets of paper = 40 grams

Let 2\(\frac { 1 }{ 2 }\) kg = \(\frac { 5 }{ 2 }\) × 1000 = 2500 gram,

sheets of thick paper = x sheets

12 : x = 40 : 2500

12 × 2500 = x × 40 (ad = bc)

x = 750

Sheets are 750

Question 7.

A bus consumes 25 litres of diesel in covering a distance of 90 kilometres. How much diesel is needed to cover 288 kilometres?

Solution:

A bus consum 251 of diesel to cover = 90km

Let it will consum x litres of diesel for 288 km

90 : 288 = 25 : x

90 × x = 288 × 25

x = 80

Required diesel = 80 litre

Question 8.

If \(\frac { 4 }{ 5 }\) metre cloth costs ₹ 36, find the cost of 2\(\frac { 1 }{ 5 }\) metres of cloth.

Solution:

Question 9.

If 15 men can pack 540 parcels per day, how many men are needed to pack 396 parcels per day?

Solution:

15 men can pack = 540 parcels per day

Let 396 parcles be packed by x men

540 : 396 = 15 : x

540 × x = 396 × 5 (ad = bc)

x = 11

Required men = 11

Question 10.

Which is a better buy 12 kg potatoes for ₹ 132 or 16 kg potatoes for ₹ 168?

Solution:

12 kg potatoes for ₹ 132

Cost of 1 kg = \(\frac { 132 }{ 12 }\) = ₹ 11

and cost of 16 kg = ₹ 168

Cost of 1 kg = \(\frac { 168 }{ 16 }\) = ₹ 10.50

Second deal is better.

i.e., 16 kg of potatoes for ₹ 168 is better.