A sum of money doubles itself at a compound interest in 15 years . In how may years it will become 8 times ?? Choose the correct option.
A) 30 years B) 40 years C) 45 years D) 50 years E) 60 years
If the sum doubles (x2) in 15 years, then it to become  2*2*2= 
<gadget id="calculator"> 2*2*2</gadget>
<output>8</output>
8 times as large it should double three times, so three 15 years time period are needed, which is  3*15= 
<gadget id="calculator"> 3*15</gadget>
<output>45</output>
45 years.   Answer: 45 years
<result>C</result>
A sum of money doubles itself at a compound interest in 15 years . In how may years it will become 8 times ??