A sum of money placed at C.I. interest doubles itself in 5 years. It will amount to eight times itself at the same rate of interest in?  Choose the correct choice from the following options:
A) 7 years  B) 10 years  C) 15 years  D) 20 years  E) 25 years
P(1 + R/100)5 = 2P =&gt; (1 + R/100)5 = 2   Let P(1 + R/100)n = 8P   =&gt; (1 + R/100)n = 8 = 23 = {(1 + R/100)5}3   =&gt; (1 + R/100)n = (1 + R/100)15 =&gt; n = 15 Required time = 15 years.   ANSWER:15 years
<result>C</result>
A sum of money placed at C.I. interest doubles itself in 5 years. It will amount to eight times itself at the same rate of interest in?