A merchant marks cloth at Rs. 50 per metre. He allows two successive discounts of 15% and 20% on this marked price. What is the net selling price per metre of the cloth?

Introduction / Context:
This is another example of successive discounts, this time on cloth priced per metre. The merchant first gives a 15 percent discount and then a further 20 percent discount on the reduced price. We are to compute the final price per metre that the customer pays. It reinforces the concept of multiplying discount factors rather than adding percentages.

Given Data / Assumptions:
- Marked price of cloth = Rs. 50 per metre.
- First discount = 15 percent on the marked price.
- Second discount = 20 percent on the price after the first discount.
- We must find the net selling price per metre after both discounts.

Concept / Approach:
A 15 percent discount means the customer pays 85 percent of the current price. Mathematically, this is a factor of 0.85. A 20 percent discount means paying 80 percent of the current price, a factor of 0.80. The final price is obtained by multiplying the marked price by both factors, in order. This is the standard method for handling multiple discounts.

Step-by-Step Solution:
Marked price per metre = Rs. 50. First discount 15% gives factor = 1 - 15 / 100 = 0.85. Price after first discount = 50 * 0.85 = Rs. 42.50. Second discount 20% gives factor = 1 - 20 / 100 = 0.80. Final selling price per metre = 42.50 * 0.80. Compute 42.50 * 0.80 = 34.00. Therefore, net price per metre = Rs. 34.00.

Verification / Alternative check:
We can also compute directly from the marked price: overall factor = 0.85 * 0.80 = 0.68. So selling price = 50 * 0.68 = 34.00. This matches the earlier stepwise calculation and confirms the answer.

Why Other Options Are Wrong:
Rs. 32.50: This is the price after a single discount of 35% or a miscalculation and does not match the correct successive discount factors.
Rs. 42.50: This is only the price after the first 15% discount, before the 20% discount is applied.
Rs. 40.00 and Rs. 36.50: These numbers do not correspond to the correct final factor of 0.68 when applied to 50.

Common Pitfalls:
Candidates sometimes add the discounts (15 + 20) to incorrectly conclude a single 35% discount. That would give 50 * 0.65 = 32.50, which is not the same as the correct answer. Another pitfall is to calculate the second discount on the original price instead of on the reduced price after the first discount. Always apply each discount to the current price in sequence.

Final Answer:
The net selling price per metre of the cloth after both discounts is Rs. 34.00.