If the simple interest on a certain sum of money for 2 years is one–fifth of the sum, then the rate of interest per annum is
Options: A) 14 % B) 7 % C) 10 % D) 15 % E) 3 %

Rationale: "explanation : let the principal ( p ) be x then , simple interest ( si ) = x / 5 time ( t ) = 2 years rate of interest per annum ( r ) = ( 100 × si ) / pt = ( 100 × ( x / 5 ) / ( x × 2 ) = 20 / 2 = 10 % answer : option c"
Answer: C