Hard
A shopkeeper marks a watch at ₹1,000 and allows a 10% discount. Even after the discount he earns a profit of 20% on the cost price. Find the cost price of the watch.
Explanation
Explanation
Step 1: Discount = 10% of ₹1,000 = ₹100, so the selling price (SP) = 1,000 − 100 = ₹900.
Step 2: Profit is 20% of cost price (CP), so SP = CP × 120/100 = 1.2 × CP.
Step 3: 1.2 × CP = 900, so CP = 900 ÷ 1.2 = ₹750.
Step 4: Check: 20% of 750 = 150 and 750 + 150 = 900 ✓.
Answer: ₹750.
PRO TIP
Re-check your working by substituting the answer back into the original question.