A text book is marked at ₹$480$ and is sold for ₹$420$. What is the percentage of discount?

Given:Marked Price ($MP$) = ₹$480$ Selling Price ($SP$) = ₹$420$ The discount amount is:
$$\text{Discount}=MP-SP=480-420=\text{₹}60$$
The discount percentage is calculated with respect to the Marked Price:
$$\text{Discount Percentage}=\frac{\text{Discount}}{MP}\times 100=\frac{60}{480}\times 100=\frac{1}{8}\times 100=12.5\%$$