When a discount of 20% is given on a lunch buffet, the profit is 42%. If the discount is 15%, then the profit is:

Let marked price of lunch buffet = Rs. 100

When discount of 20% is given, => Selling price of ticket = $$\frac{(100 - 20)}{100} \times 100 = Rs. 80$$

Let cost price = $$Rs. x$$

=> Profit % = $$\frac{80 - x}{x} \times 100 = 42$$

=> $$\frac{80 - x}{x} = \frac{42}{100} = \frac{21}{50}$$

=> $$4000 - 50x = 21x$$

=> $$21x + 50x = 71x = 4000$$

=> $$x = \frac{4000}{71} = $$ Rs. $$56.33$$

If discount is 15%, => Selling price = $$\frac{(100 - 15)}{100} \times 100 = Rs. 85$$

=> Profit % = $$\frac{85 - 56.33}{56.33} \times 100$$

= $$\frac{2867}{56.33} \approx 50.875\%$$

=> Ans - (B)