When the price of a radio was reduced by 20%, its sale increased by 80%. What was the net effect on the sale?  Choose the most appropriate option.
A) 44 % increase B) 44 % decrease C) 66 % increase D) 75 % increase E) none of these

Rationale: let the original price be x and sale be of y units . then , the revenue collected initially = x × y now , new price = 0.8 x , new sale = 1.8 y then , new revenue collected = 1.44 xy % increase in revenue = 0.44 xy / xy × 100 = 44 % increase answer a
Answer: A