A shopkeeper sells wheat at a quoted profit of 10% and also uses weights that are 20% short (he delivers only 0.8 kg when billing 1 kg). What is his total gain percentage on true cost?

Introduction / Context:
This combines an explicit price margin with a short-weight trick. The overall profit is computed relative to the cost of the actual quantity delivered, not the billed quantity.

Given Data / Assumptions:

• True cost per kg = C.
• Quoted price profit = 10% ⇒ billed price per 1 “kg” = 1.10 * C.
• Delivered quantity per billed kg = 0.8 kg.

Concept / Approach:
For one billed kilogram: revenue = 1.10C; cost of delivered goods = 0.8C. Profit% on cost = (revenue − cost)/cost * 100 = (1.10C − 0.8C)/(0.8C) * 100.

Step-by-Step Solution:
Profit = 0.30CCost base = 0.80CProfit% = 0.30C / 0.80C * 100 = 37.5%

Verification / Alternative check:
On 4 kg actually delivered (billed as 5 kg), revenue = 5 * 1.10C = 5.5C; cost = 4C; profit = 1.5C; profit% = 1.5/4 * 100 = 37.5%.

Why Other Options Are Wrong:
30% ignores short-weight; 88% is far too high; “None” is invalid.

Common Pitfalls:
Using selling price as the profit base; overlooking that short-weight increases effective price per true kg.

Final Answer:
37.5%