Profit and Loss – Combining different purchase rates, single selling rate: A fruit seller buys 700 oranges at ₹ 500 per 100 oranges and 500 more oranges at ₹ 700 per 100 oranges. He sells all oranges at ₹ 84 per dozen. What is his profit percentage on the whole?

Introduction / Context:
This is a weighted-average cost question. Different purchase rates for two lots must be combined to get the overall cost. Then a single selling rate is applied to all units to find total revenue and profit percentage.

Given Data / Assumptions:

• Lot 1: 700 oranges at ₹ 500 per 100 ⇒ ₹ 5 each
• Lot 2: 500 oranges at ₹ 700 per 100 ⇒ ₹ 7 each
• Selling rate: ₹ 84 per dozen ⇒ ₹ 7 per orange

Concept / Approach:
Total cost = sum of lots’ costs. Total revenue = total oranges * selling price per orange. Profit% = (Revenue − Cost) / Cost * 100.

Step-by-Step Solution:
Cost of first lot = 700 * 5 = ₹ 3500Cost of second lot = 500 * 7 = ₹ 3500Total cost = ₹ 7000Total oranges = 1200 ⇒ revenue = 1200 * ₹ 7 = ₹ 8400Profit = 8400 − 7000 = ₹ 1400 ⇒ Profit% = 1400 / 7000 * 100 = 20%

Verification / Alternative check:
The average cost per orange is ₹ 7000 / 1200 ≈ ₹ 5.8333; selling at ₹ 7 yields roughly ₹ 1.1667 per orange, which is 20% of ₹ 5.8333.

Why Other Options Are Wrong:
40% and 30% overstate the gain; 10% understates it; 25% does not match the exact arithmetic.

Common Pitfalls:
Taking a simple average of the two purchase rates without weighting by quantities.

Final Answer:
20%