Balbharti Maharashtra State Board Class 7 Maths Solutions covers the 7th Std Maths Practice Set 37 Answers Solutions Chapter 37 Direct Proportion and Inverse Proportion.

## Direct Proportion and Inverse Proportion Class 7 Practice Set 37 Answers Solutions Chapter 9

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.