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?  Choices
A) 22	B) 28	C) 15	D) 18	E) 11
Explanation:   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
<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?