An appliance dealer sold a refrigerator costing ₹18000 at a profit of 15% and, the same week, a washing machine costing ₹12000 at a loss of 15%. On the two sales together he made:

Profit on the refrigerator = $18000\times 0.15$ = ₹2700; loss on the washing machine = $12000\times 0.15$ = ₹1800. Net gain ₹900 on an outlay of ₹30000 = 3%. (Equal percentages do NOT cancel here, because the 15% gain rides on the larger cost and the 15% loss on the smaller — that is why 'neither a profit nor a loss' fails. The 3% would turn into a loss only if the dearer item were the one sold at a loss, and 15% is merely the rate that appears on both sales.)