At what rate per cent per annum will a sum of money double in 8 years?

The difference between the simple interest and the compound interest on a certain amount at 5% for two years is 25, what is the amount?

The amount ₹2,100 became ₹ 2,352 in 2 years at simple interest. If the interest rate is decreased by 1%, what is the new interest?

In what time will ₹8000, at 3% per annum, produce the same interest as ₹6000 does in 5 years at 4% simple interest is? 

Atm of ₹2.400. amounts to ₹3,264 in 4 years at a certain rate of simple interest. If the rate of interest is increased by 1% the same sum in the same time would amount to-

A sum of ₹ 800 amounts to ₹ 920 in 3 years at the simple interest rate. If the rate is increased by 3 % p.a., what will be the sum amount to in the same period? 

A person invests money in three different schemes 6 years, 10 years and 12 years at 10%, 12% and 15% simple interest respectively. At the completion of each scheme, he gets the same interest. The ratio of his investment is