Claims to sell at cost but uses 920 g as “1 kg” — find true gain A dealer professes to sell at cost price but uses a 920 g weight instead of 1 kg. What is his gain percentage?

Introduction / Context:
Short-weight tricks produce profit even when the posted price equals cost price. Charging for 1 kg while delivering only 920 g yields a gain because the seller's cost is incurred on a smaller mass than billed.

Given Data / Assumptions:

• Charge as if 1 kg is delivered, at cost price per kg.
• Actual delivered mass = 0.92 kg.
• Uniform cost per true kg.

Concept / Approach:
If CP per true kg = C, then revenue for a “1 kg” sale = C. Actual cost incurred = 0.92C. Profit fraction on cost = (C − 0.92C)/(0.92C) = (0.08/0.92) = 8/92 = 2/23. Convert to percent for the answer.

Step-by-Step Solution:
Profit fraction = 1/0.92 − 1 = (1 − 0.92)/0.92 = 0.08/0.92 = 2/23.Profit% = (2/23) * 100 = 200/23 % = 8 16/23%.

Verification / Alternative check:
Numerical check: Take C = ₹100: charge ₹100 but incur cost on 0.92 kg = ₹92; profit = ₹8; profit% = 8/92 * 100 ≈ 8.6956% = 8 16/23%.

Why Other Options Are Wrong:
Other percentages do not equal 200/23% and therefore do not match a 920 g short weight.

Common Pitfalls:
Using 8% directly instead of 8/92, or confusing percent of SP with percent of CP.

Final Answer:
8 16/23% gain