A dealer gains 20% by selling an article at 25% discount on its marked price. If the cost price of the article is decreased by 15%, how much discount percentage should he now given on the same marked price so as to earn the same percentage of profit as before?

Answer: Option C

Let cost price = 100
Selling price = 120% of 100 = 120
Marked price = 120 × $$\frac{100}{75}$$ = 160

New cost price = 100 - 15 = 85
New selling price = 85 × $$\frac{120}{100}$$ = 102
Discount = 160 - 102 = 58
Discount = $$\frac{58}{160}$$ × 100 = 36.25%