Inferring marked price from profit change with discount tweak: A shirt is sold with a 7% discount. If the discount had been 9%, the shopkeeper’s profit would have been ₹15 less. What is the marked price of the shirt?

Introduction / Context:
The change in profit from changing the discount rate by 2 percentage points equals 2% of the marked price, because cost stays fixed and selling price changes by 2% of MRP. Using the given rupee change in profit, you can solve for the marked price directly without needing cost or initial profit explicitly.

Given Data / Assumptions:

• Discount1 = 7% ⇒ SP1 = 0.93M.
• Discount2 = 9% ⇒ SP2 = 0.91M.
• Profit difference = SP1 − SP2 = ₹15.

Concept / Approach:
Since cost is unchanged, the change in profit equals the change in selling price. Therefore, (0.93M − 0.91M) = 0.02M = ₹15. Solve for M directly.

Step-by-Step Solution:

Verification / Alternative check:
At M = 750, SP1 = 697.50, SP2 = 682.50; difference = ₹15, matching. The cost cancels in the difference, hence not required.

Why Other Options Are Wrong:
₹720, ₹712.50, ₹600, ₹840 do not satisfy a ₹15 change when discount shifts by 2 percentage points.

Common Pitfalls:
Trying to compute cost or initial profit unnecessarily; focusing on the selling price change is faster and cleaner.

Final Answer:
₹ 750