If an amount doubles automatically in 8 years, then what is the interest rate?

If the volumes of two cubes are in the ratio 27 : 64 and then the ratio of their total surface area is 

A lent some money from B and paid 1,573 after$$ {1{1\over 2}}$$ yr . Also B lent some money from A and paid 1444.50 after 6 months. If they want to settle the account forthwith, keeping 14 % as the rate of interest, then who should pay whom and how much?

The single discount which is equivalent to three successive discounts of 25%, 20% and 10% is-

If a trader finds out that his profit is equal to 20 percent of the selling price, then his actual profit is.

Direction: Study the following information and answer the related questions. P, Q, R, S, T, A, B, C, D and E are employees of a company. A table shows the average age of any two employees of the company. The average age of A and B is 27.5.
i.e. average age of A & P is given as (A+P)/2=39.5

What is the age of T?

A works 7 hours a day at the rate of 180 per hour. B works 5 hours a day at the rate of 160 per hour. What is the ratio of daily earnings of A and B?

Three numbers are such that the average of first two numbers is 2, the average of the last two numbers is 3 and the average of the first and the last numbers is 4, then the average of three numbers is equal to.