At what rate of annual simple interest,a certain sum will amount to four times in 15 year?
Choose the correct choice from the following options.
A) 15% B) 17.5% C) 20% D) 25% E) 35%
r=?   t=15 yrs   SI=p*r*t/100   Amount = SI+p = 4p   (p*r*15/100)+p = 4p   p(15r/100 + 1) = 4p   15r + 100 = 400   15r = 300   r = 20%   ANSWER:20%
<result>C</result>
At what rate of annual simple interest,a certain sum will amount to four times in 15 year?