If the simple interest on a certain sum of money is 4/25 of the sum and the rate percent equals the number years, then the rate of interest per annum is ?

Let the principal be Rs.x, then the simple interest (I) = (4 / 25 )x.
The rate of interest per annum be r% then time (T) = r years
R = ( 100 * I ) / ( P * T )
r = ( 100 * ( 4/25 ) x ) / ( x * r )
r² = 400 / 25
r = 20 / 5
= 4 %