## Maharashtra State Board Class 7 Maths Solutions Chapter 9 Direct Proportion and Inverse Proportion Practice Set 37

Question 1.

If 7 kg onions cost Rs 140, how much must we pay for 12 kg onions?

Solution:

Let the cost of 12 kg onions be Rs x.

The quantity of onions and their cost are in direct proportion.

∴ \(\frac{7}{140}=\frac{12}{x}\)

∴ 7x = 12 × 140 ….(Multiplying both sides by 140x)

∴ x = \(\frac { 12\times 140 }{ 7 }\)

= 240

We must pay Rs 240 for 12 kg onions.

Question 2.

If Rs 600 buy 15 bunches of feed, how many will Rs 1280 buy?

Solution:

Let the bunches of feed bought for Rs 1280 be x.

The quantity of feed bought and their cost are in direct proportion.

∴ \(\frac{600}{15}=\frac{1280}{x}\)

∴ 600x = 1280 × 15 …. (Multiplying both sides by 15x)

∴ \(x=\frac{1280 \times 15}{600}=32\)

∴ 32 bunches of feed can be bought for Rs 1280.

Question 3.

For 9 cows, 13 kg 500 g of food supplement are required every day. In the same proportion, how much will be needed for 12 cows?

Solution:

Let the food supplement required for 12 cows be x kg.

The quantity of food supplement required and the number of cows are in direct proportion.

∴ \(\frac{13 \mathrm{kg} 500 \mathrm{gram}}{9}=\frac{x \mathrm{kg}}{12}\)

∴ \(\frac{13.5}{9}=\frac{x}{12}\) ….(13 kg 500 gram = 13.5 kg)

∴ 13.5 × 12 = 9x ….(Multiplying both sides by 9 x 12)

∴ \(\frac{13.5 \times 12}{9}=x\)

∴ x = 18

∴ The food supplement required for 12 cows is 18 kg.

Question 4.

The cost of 12 quintals of soyabean is Rs 36,000. How much will 8 quintals cost?

Solution:

Let the cost of 8 quintals of soyabean be Rs x.

The quantity of soyabeans and their cost are in direct proportion.

∴ \(\frac{12}{36000}=\frac{8}{x}\)

∴ 12x = 8 × 36000 ….(Multiplying both sides by 36000x)

∴ \(x=\frac{8 \times 36000}{12}=24000\)

∴ The cost of 8 quintals of soyabean is Rs 24000.

Question 5.

Two mobiles cost Rs 16,000. How much money will be required to buy 13 such mobiles ?

Solution:

Let the cost of 13 mobiles be Rs x.

The quantity of mobiles and their cost are in direct proportion.

∴ \(\frac{2}{16000}=\frac{13}{x}\)

∴ 2x = 13 × 16000 ….(Multiplying both sides by 16000x)

∴ \(x=\frac{13 \times 16000}{2}=104000\)

∴ Rs 104000 will be required to buy 13 mobiles.