By selling 45 oranges for Rs. 40, a man loss 20%. how many should he sell for Rs. 24 so as to gain 20% in the transaction?

Cost price for 45 oranges - 20% = Rs. 40.
∴ Cost price for 45 oranges = Rs. 50.
When he sells for Rs. 24 his gain is 20%, hence cost price is Rs 20.
Number of oranges = (20 x 45)/50 = 18