The sum of money at compound interest amounts to thrice itself in 3 years. In how many years will it be 9 times itself?  Pick:
A) 5 years B) 7 years C) 9 years D) 6 years E) 12 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?