By selling 36 oranges, a vender loses the selling price of 4 orange. His loss per cent is?

∵ Loss = C.P. of 36 oranges - S.P. of 36 oranges
⇒ S.P. of 4 = C.P. of 36 - S.P.of 36
∴ S.P.of 40 = C.P. of 36
Let C.P. of each oranges = Re. 1
⇒ C.P.of 40 = Rs. 40
⇒ S.P. of 40 = Rs. 36
∴ Loss = (4 / 40 ) x 100 % = 10%