In which of the following discount percentage will be maximum?

Correct option is C

Given:
Option A: Marked Price = ₹3200, Selling Price = ₹2800
Option B: Marked Price = ₹4000, Selling Price = ₹3600
Option C: Marked Price = ₹2400, Selling Price = ₹2000
Option D: Marked Price = ₹2800, Selling Price = ₹2400 
Formula Used:
$$\text{Discount \%} = \left( \frac{\text{Marked Price} - \text{Selling Price}}{\text{Marked Price}} \right) \times 100\\[10pt]$$ 
Solution:

 $$\textbf{Option A:} \\\text{Discount \%} = \left( \frac{3200 - 2800}{3200} \right) \times 100 = \frac{400}{3200} \times 100 = 12.5\%\\[10pt]\textbf{Option B:} \\\text{Discount \%} = \left( \frac{4000 - 3600}{4000} \right) \times 100 = \frac{400}{4000} \times 100 = 10\%\\[10pt]\textbf{Option C:} \\\text{Discount \%} = \left( \frac{2400 - 2000}{2400} \right) \times 100 = \frac{400}{2400} \times 100 \approx 16.67\%\\[10pt]\textbf{Option D:} \\\text{Discount \%} = \left( \frac{2800 - 2400}{2800} \right) \times 100 = \frac{400}{2800} \times 100 \approx 14.29\%\\[10pt]$$ 
Option C will provide the maximum discount.