If the simple interest on a certain sum of money for 8 years is one–fifth of the sum, then the rate of interest per annum is Options:  A) 4.1 %  B) 7 %  C) 2.5 %  D) 2.8 %  E) 3 %

Rationale: explanation : let the principal ( p ) be x then , simple interest ( si ) = x / 5 time ( t ) = 8 years rate of interest per annum ( r ) = ( 100 × si ) / pt = ( 100 × ( x / 5 ) / ( x × 8 ) = 20 / 8 = 2.5 % answer : option c
Answer: C