A shopkeeper wants to make some profit by selling rice. He contemplates about various methods. Which of the following would maximise his profit? I. Sell rice at 15% profit. II. Use 850 g of weight instead of 1 kg. III. Mix 15% impurities in rice and selling rice at cost price. IV. Increase the price by 7.5% and reduce weights by 7.5%.

Method I: 15% profit. Method II: 850g instead of 1000g means selling 850g at 1000g price, so profit = (1000-850)/850 = 17.65%. Method III: 15% impurities means selling only 85% rice at full price, so profit = (100-85)/85 = 17.65%. Method IV: 7.5% price increase and 7.5% weight decrease gives approximately 15.4% profit. Method II gives the highest profit at 17.65%.