If x varies inversely as y and x = 20 when y = 600, find y when x = 400.

Which of the following vary directly and which vary inversely with each other and which are neither of the two?

(i) Number of students in a hostel and consumption of food.

(ii) Area of the walls of a room and the cost of white washing the walls.

(iii) The number of people working and the quantity of work.

(iv) Simple interest on a given sum and the rate of interest.

(v) Compound interest on a given sum and the sum invested.

Which of the following vary directly and which vary inversely with each other and which are neither of the two?

(i) The quantity of rice and its cost.

(ii) The height of a tree and the number of years.

(iii) Increase in cost and number of shirts that can be purchased if the budget remains the same.

(iv) Area of land and its cost.

(v) Sales Tax and the amount of the bill.

The variable x varies directly as y and x = 80 when y = 160, What is y when x is 64.

l varies directly as m and l is equal to 5, when , find l when .