A sum of money placed at compound interest triples itself in 9 year. In how many years will if amount to 243 times itself?

In 3 years ₹ 3000 amounts to ₹ 3993 at x % compound interest, compounded annually. The value of x is 

The compound interest earned in two years at 8 % per annum is 3993.6 . What is the sum invested? 

What is compound interest accrued on an amount of Rs 45000 in 2 yr @ 9% per annum ? 

If the compound interest rate is 20% per annum compounded half yearly, then what will be the interest for two years on the principal of Rs. 100000?

A sum of Rs 5,000 amounts to Rs 7,200 in 8 years at a certain rate percent p.a, interest compounded yearly. What will be the compound interest on a sum of Rs.6,550 in 4 years at the same rate of interest?

A certain sum increases by 50 % in 5 years. Three sums x, y and z are lent for 10, 15 and 20 years respectively. If amount on each sum is equal, then find the ratio of x, y and z.