Farhan barters 60 kg of rice that cost him ₹80 per kg for 50 kg of cashew whose market value is ₹120 per kg. His gain percent on the deal is:

The goods he gives up cost $60\times 80$ = ₹4800; the goods he receives are worth $50\times 120$ = ₹6000. Gain = ₹1200 on a cost of ₹4800 = 25%. (Dividing ₹1200 by the ₹6000 received gives the trap 20% — gain percent is always measured on cost.)