Mohan bought 30 books for Rs.3000 and sold them at a profit equal to the selling price of 6 books. The selling price of 1 book is:

130 124 125 140

124

S.P. of 30 - C.P. of 30 = S.P. of 6 (profit) S.P. of 24 = C.P. of 30 C.P. of 30 = Rs. 3000 (given) Therefore, S.P. of 24 = Rs. 3000 S.P. of 1 = Rs. 124/-