A shopkeeper buys 150 calculators at Rs 250 each and spends Rs 2500 on transportation and packing. The marked price per calculator is Rs 320, and he offers a 5% discount. Compute the overall profit percentage.

Introduction:
This problem combines bulk purchase cost, additional overhead expenses, marked price, and discount to test total profit percentage computation. Always aggregate all costs into the effective cost price before comparing with total revenue from sales.

Given Data / Assumptions:

• Quantity = 150 calculators.
• Base purchase cost per unit = Rs 250.
• Additional expense (transport and packing) = Rs 2500.
• Marked price per unit = Rs 320, discount = 5%.

Concept / Approach:
Total cost = (unit cost * quantity) + overhead. Selling price per unit after discount = marked price * (1 - discount). Total revenue = that selling price times quantity. Profit percentage = (revenue - cost) / cost * 100.

Step-by-Step Solution:
Total base cost = 150 * 250 = 37500Add expense = 2500 ⇒ Total cost = 37500 + 2500 = 40000SP per unit after 5% discount = 320 * 0.95 = 304Total revenue = 150 * 304 = 45600Profit = 45600 - 40000 = 5600Profit% = 5600 / 40000 * 100 = 14%

Verification / Alternative check:
Average effective cost per unit = 40000 / 150 ≈ 266.67; margin per unit = 304 - 266.67 ≈ 37.33. Percentage = 37.33 / 266.67 * 100 ≈ 14% (minor rounding aligns with exact totals).

Why Other Options Are Wrong:

• 20% and 16%: overstate the margin by ignoring overhead or miscomputing discount.
• 15%: close but not exact; exact computation gives 14%.

Common Pitfalls:

• Forgetting to include transportation and packing in cost.
• Applying the 5% discount to cost instead of to the marked price.

Final Answer:
14%