A sum of money doubles itself at compound interest in 15 years. In how many years will it become eight times? Select the correct option.
A) 45 years  B) 40 years  C) 42 years  D) 38 years  E) None
P { 1 + R/100 }^15 = 2P ie [ 1 + R/100]^15 = 2 … (i) Let P[ 1 + R/100]^n = 8P [ 1 + R/100]^n =8 2^3 = { [1 + R/100]15 }^3 [ 1 + R/100]^n = [ 1 + R/100]^45 i.e n=45 Thus required time = 45 years   45 yearsnswer 45 years
<result>A</result>
A sum of money doubles itself at compound interest in 15 years. In how many years will it become eight times?