The simple interest on a certain sum of money for 3 years at 5% per annum is ₹ 1200. Find the amount due and the compound interest on this sum of money at the same rate and after 2 years, interest is reckoned annually.

Nikita invests ₹ 6000 for two years at a certain rate of interest compounded annually. At the end of first year it amounts to ₹ 6720. Calculate :

(a) the rate percent (i.e. the rate of growth)

(b) the amount at the end of the second year.

A certain sum of money doubles itself at a given rate in 8 years compounded yearly. In how many years will it be four times at the same rate compounded yearly ?

Mr. Sharma wants to divide ₹ 1,68,200 between his two sons who are 16 years and 18 years old respectively, in such a way that the sum invested at the rate of 5% p.a compound interest annually will give the same amount to each when they attain the age of 21 years. How much should he divide the sum ?