Question

Successive discounts of $10$% and $20$% are equivalent to a single discount of

• A. $30$%
• B. $15$%
• C. $72$%
• D. $28$%
• E. None of these

Answer 1

Answer: (D)

$28$%

Let $P$ be the original price. Then a discount of $10$% gives a new price $10-.1P=..9P$. Following this by a discount of $20$% we have
$.9P=.2\left(.9P\right)=.72P$.
Thus the net discount is $P-.72P=.28P$ or $28$%; or
Net discount $=d_1+d_2-d_1{d}_2=\frac{10}{100}+\frac{20}{100}-\frac{2}{100}=28$%.