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 Pick one:
A) 17 years
B) 87 years
C) 15 years
D) 16 years
E) 19 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