Secondary School (English Medium) (5 to 8) Class 8 - CBSE Question Bank Solutions for Mathematics

Which of the following quantities vary inversely as other?

 Journey (x km) undertaken by a car and the petrol (y litres) consumed by it.

It is known that for a given mass of gas, the volume v varies inversely as the pressure p. Fill in the missing entries in the following table:

A work force of 50 men with a contractor can finish a piece of work in 5 months. In how many months the same work can be completed by 125 men? 

A work-force of 420 men with a contractor can finish a certain piece of work in 9 months. How many extra men must he employ to complete the job in 7 months?

1200 men can finish a stock of food in 35 days. How many more men should join them so that the same stock may last for 25 days?

In a hostel of 50 girls, there are food provisions for 40 days. If 30 more girls join the hostel, how long will these provisions last?

A car can finish a certain journey in 10 hours at the speed of 48 km/hr. By how much should its speed be increased so that it may take only 8 hours to cover the same distance?

1200 soldiers in a fort had enough food for 28 days. After 4 days, some soldiers were transferred to another fort and thus the food lasted now for 32 more days. How many soldiers left the fort?

Three spraying machines working together can finish painting a house in 60 minutes. How long will it take for 5 machines of the same capacity to do the same job?

A group of 3 friends staying together, consume 54 kg of wheat every month. Some more friends join this group and they find that the same amount of wheat lasts for 18 days. How many new members are there in this group now?

55 cows can graze a field in 16 days. How many cows will graze the same field in 10 days?

18 men can reap a field in 35 days. For reaping the same field in 15 days, how many men are required?

A person has money to buy 25 cycles worth Rs 500 each. How many cycles he will be able to buy if each cycle is costing Rs 125 more?

Raghu has enough money to buy 75 machines worth Rs 200 each. How many machines can he buy if he gets a discount of Rs 50 on each machine?

If x and y vary inversely as other and x = 3 when y = 8, find y when x = 4 .

If x and y vary inversely as other and x = 5 when y = 15, find x when y = 12 .

If x and y vary inversely as other and  x = 30, find y when constant of variation = 900.

If x and y vary inversely as other and y = 35, find x when constant of variation = 7.

Construct a parallelogram PQRS such that PQ = 5.2 cm, PR = 6.8 cm and QS = 8.2 cm.