A dishonest shopkeeper makes a cheating of 20% at the time of buying the goods and 40% cheating at the time of selling the goods. He promises to sell his goods at 10% loss. Find the profit %.

80%

Let the actual weight = 1000 gm

Total weight for him = 1000 × \(\frac{120}{100}\) = 1200 gm

Total weight for him on SP = 1200 × \(\frac{100}{60}\) = 2000 gm

Sell goods at 10% loss = 2000 × \(\frac{90}{100}\) = 1800

Actual CP = 1000

Profit = 1800 - 1000 = 800

Profit % = \(\frac{800}{1000}\) × 100 = 80%