A sum of money place at compound interest doubles itself in 6 years. In how many years will it amount to eight times itself?
Pick:	A) 15 years	B) 11 years	C) 12 years	D) 18 years	E) 19 years
100 ---- 200 ---- 6   400 ---- 6   800 ---- 6   ------   18 years   Answer: 18 years
<result>D</result>
A sum of money place at compound interest doubles itself in 6 years. In how many years will it amount to eight times itself?