A car mechanic purchased four old cars for Rs. 1 lakh in total and spent another Rs. 2 lakh on maintenance and repairs of these four cars. He has already sold one of the cars for Rs. 1.2 lakh. At what average selling price should he sell each of the remaining three cars to make an overall profit of 50% on his total investment?

Introduction / Context:
This question is a mixture of total cost accounting and average selling price. The mechanic invests in four cars and additional repairs, sells one car, and wants a target overall profit percentage. We are asked to find the average selling price required for the remaining cars so that the total profit objective is achieved. It is a typical example of combining total cost, partial sales, and average revenue.

Given Data / Assumptions:

• Purchase cost of four old cars = Rs. 1 lakh.
• Repairs and maintenance for all four cars = Rs. 2 lakh.
• Total investment = Rs. 3 lakh.
• One car is already sold for Rs. 1.2 lakh.
• Mechanic wants an overall profit of 50% on the total investment.
• We must find the average selling price of each of the three remaining cars.

Concept / Approach:
A 50% profit on the total cost means that the total revenue from selling all four cars must be 1.5 times the total investment. From this target total revenue, we subtract the amount already received from the first car. The remainder must come from the three remaining cars. Dividing that remainder by 3 gives the required average selling price per car.

Step-by-Step Solution:
Step 1: Total purchase cost of cars = Rs. 1 lakh, repairs = Rs. 2 lakh.Step 2: Total investment = 1 + 2 = Rs. 3 lakh.Step 3: Required total revenue for 50% profit = 1.5 * 3 lakh = Rs. 4.5 lakh.Step 4: Revenue already received from one car = Rs. 1.2 lakh.Step 5: Revenue still needed from remaining three cars = 4.5 lakh - 1.2 lakh = Rs. 3.3 lakh.Step 6: Required average selling price per remaining car = 3.3 lakh / 3 = Rs. 1.1 lakh.

Verification / Alternative check:
If each of the three remaining cars is sold for Rs. 1.1 lakh, revenue from them = 3 * 1.1 lakh = Rs. 3.3 lakh.Total revenue from all four cars = 1.2 lakh + 3.3 lakh = Rs. 4.5 lakh.Total profit = total revenue - total investment = 4.5 lakh - 3 lakh = Rs. 1.5 lakh, which is 50% of Rs. 3 lakh.

Why Other Options Are Wrong:
Average prices such as Rs. 1.5 lakh or Rs. 1.65 lakh would give profits higher than 50%. Values like Rs. 1.2 lakh or Rs. 1.3 lakh would yield total revenues that do not align exactly with a 50% overall profit. Only Rs. 1.1 lakh produces precisely the required 50% profit on the combined investment.

Common Pitfalls:
Some learners incorrectly compute profit on only the purchase cost of the cars and ignore repair expenses, underestimating total investment. Others mistakenly try to allocate equal profit per car instead of working from the total revenue target. Focusing on overall cost and total profit first makes the reasoning much clearer.

Final Answer:
The mechanic should sell each of the remaining three cars at an average price of Rs. 1.1 lakh.