Solution :-
He gets 25% profit on the selling price.
Let SP = x and 25 % of x = 25/ 100 * x = > x/ 4 , So we got profit = x/ 4
So , CP = x-(x/4) = Rs. 3x/4. ( C.P = S.P - Profit )
Hence,
%gain = {(x/4) / (3x/4)}*100 = 100/3 ( formula of gain% = gain / c.p *100 )
= 33(1/3). Answer.