If 21 cows eat equal to 15 oxen, how many cows will eat equal to 25 oxen?

The length of a rectangle is 2 cms more than its width. If the perimeter is 36 cms., then the area is

The exponent in (2ab) ^-2.6 is

Find x, if 25 : x = x : 4

Side of a square is 4x. Its area is

A water tank contains 2/5 part water. When 250 litres of water is taken out, there remains 3/20 part of water in the tank. What is the volume of the tank?