The radii of two right circular cylinders are in the ratio 4:3 and their heights are in the ratio 7:4 then the ratio of their curved surface areas is in the ratio

A radio active element "X" with a half life of 2 hours decay giving a stable element "Y". After a time of t hours the ratio of atoms is 1:7 then, the value of 

If 1/2(2x+3Y)+12/7(3x-2Y) = 1/2 and 7/2x+3y+4/3x-2y=2 then values of x and y are respectively.

A school boy walks from his house to school at the rate of 4 kmph. He reaches the school 20 minutes earlier than the schedule time. If he walks at the rate of 3 kmph, he reaches the school 20 minutes late. What is the distance of the school from his house

A number is increased by 10% and then decrease by 10%. Find the net decrease percent.

Find the compound interest on Rs. 31250 at 8% p.a for 3 years compounded annually