At what rate of simple interest certain amount will double itself in 8 years?
(a) 12%
(b) 12 ½%
(c) 13%
(d) 15%
Answer: (b) 12 1/2%
Solution:-
Let the principal be X.
Then, Simple Interest = X
According to the question,
Rate of Interest = (100 x X)/(X x 8)
= 12.5%
Hence, the correct answer is option (b) 12 1/2%.