A dealer marks his goods 20% above cost price and then allows a discount of 30% on the marked price. He suffers a loss of what percent?

Take the cost as ₹100. The marked price is ₹120 and the selling price is $120\times 0.70$ = ₹84, so the loss is ₹16 on ₹100 = 16%. (Subtracting 30 − 20 to get 10% treats both percentages as if they were taken on the cost, but the 30% is taken on the larger marked price — ₹36 off, not ₹30.)