Q1
If the cost price is 80% of the selling price, then what is the profit in percentage?
Answer: B
Asked: profit % when CP is 80% of SP.
Key idea: profit % is always calculated on the cost price.
Let SP = 100. Then CP = 80.
Profit = 100 − 80 = 20.
Profit % = \( \frac{20}{80} \times 100 = 25\% \).
Common trap: 20% is the profit as a share of the selling price (20 out of 100). That is not the profit percentage.
Faster: SP/CP = 100/80 = 5/4. So SP is 1/4 more than CP, which means 25% profit.
Answer: 25% (option 2)