Two successive discount of 10% and 20% are equivalent to a single discount of:

Answer: Option B

Use Formula,
Equivalent Discount = (A + B) - $$\frac{\text{AB}}{100}$$ where A = First Discount, B =Second Discount.
Equivalent Discount = (20 + 10) - $$\frac{20\times 10}{100}$$
Equivalent Discount = 30 - 2 = 28%

Graphic Change Method
100 == 20%(disc.) ⇒ 80 == 10%(disc.) ⇒ 72
Equivalent discount = 28%