A certain sum of money doubles itself in 20 years in how much many years will it trible itself at the same rate?
Choose the correct answer:
A) 20 years  B) 76 years  C) 88 years  D) 40 years  E) 11 years
100 ---- 100 --- 20   100 --- 20   --------------------   300 ---- 40 years   Answer: 40 years
<result>D</result>
A certain sum of money doubles itself in 20 years in how much many years will it trible itself at the same rate?