The sum of money at compound interest amounts to thrice itself in 3 years. In how many years will it be 9 times itself? Select the correct option:  A) 7 years  B) 5 years  C) 4 years  D) 6 years  E) 3 years
100 ---- 300 --- 3   900 --- 3   ----   6 years   Answer:6 years
<result>D</result>
The sum of money at compound interest amounts to thrice itself in 3 years. In how many years will it be 9 times itself?