Puneet purchases 5 dozens of oranges at the rate of Rs 120 per dozen and sells every orange for Rs 11.50. What is his overall profit percentage on this transaction?

Introduction / Context:
This problem is a straightforward profit and loss question involving buying oranges in dozens and selling them individually. It checks whether you can convert between dozens and single units, compute total cost price, total selling price, and then use the standard profit percentage formula. Such questions are very common in competitive exams and help you practice careful handling of units and percentages.

Given Data / Assumptions:

• Puneet purchases 5 dozens of oranges.
• Cost price is Rs 120 per dozen.
• He sells each orange for Rs 11.50.
• We assume there is no wastage or spoilage; all oranges are sold.
• We need the overall profit percentage on the entire deal.

Concept / Approach:
The key ideas are:

• Convert dozens to number of oranges: 1 dozen = 12 oranges.
• Total cost price (CP) = number of dozens * price per dozen.
• Total selling price (SP) = number of oranges * selling price per orange.
• Profit = SP - CP.
• Profit percentage = (Profit / CP) * 100.

Working systematically with totals instead of per unit simplifies the calculations and reduces mistakes.

Step-by-Step Solution:
Step 1: Compute total number of oranges = 5 dozens * 12 = 60 oranges. Step 2: Compute total cost price = 5 * 120 = Rs 600. Step 3: Compute total selling price = 60 * 11.50 = Rs 690. Step 4: Profit = SP - CP = 690 - 600 = Rs 90. Step 5: Profit percentage = (90 / 600) * 100. Step 6: (90 / 600) = 0.15, so profit percentage = 0.15 * 100 = 15%.

Verification / Alternative check:
We can also think in terms of per dozen profit. One dozen contains 12 oranges. At Rs 11.50 per orange, selling price per dozen is 12 * 11.50 = Rs 138. Cost price per dozen is Rs 120. So profit per dozen is Rs 18. Then profit percentage per dozen is (18 / 120) * 100 = 15%. Since all dozens are identical, the overall profit percentage remains 15%. This matches our earlier result, confirming the calculation is consistent.

Why Other Options Are Wrong:
18%: This would require profit to be 18% of Rs 600, that is Rs 108, but actual profit is Rs 90 only.
30%: A 30% profit on Rs 600 would be Rs 180, which is much higher than the actual profit of Rs 90.
12%: A 12% profit would be (12 / 100) * 600 = Rs 72, which does not match the actual profit.
Therefore, none of these values fit the correct profit computation, leaving 15% as the only valid answer.

Common Pitfalls:
Students sometimes forget to convert dozens to units and mistakenly multiply by 5 instead of 60 when computing selling price. Another common error is to mix up profit percentage on selling price versus cost price, but here the question clearly asks for profit percentage on cost price. Careless handling of the decimal 11.50 can also cause mistakes, so it is important to multiply carefully. Always recompute total cost and total selling price to avoid such errors.

Final Answer:
The overall profit percentage earned by Puneet on selling the oranges is 15%.