Profit and Loss — The selling price of 20 articles equals the cost price of 22 articles. Determine the gain percentage.

Introduction / Context:
When SP for some count equals CP for a different count, the profit% can be derived by comparing SP per unit with CP per unit.

Given Data / Assumptions:

• 20 * SP_per_unit = 22 * CP_per_unit

Concept / Approach:
Rearranging gives SP_per_unit / CP_per_unit = 22/20 = 1.10, which means SP is 10% above CP ⇒ 10% profit.

Step-by-Step Solution:

Verification / Alternative check:
Assume CP_unit = ₹ 100 ⇒ SP_unit = ₹ 110 ⇒ For 20 units SP = ₹ 2200 = 22 * 100 = cost of 22 units, consistent.

Why Other Options Are Wrong:
12%, 11%, 9%, and 8% do not match the strict ratio 22/20 = 1.10.

Common Pitfalls:
Taking difference 22 − 20 = 2 then reporting 2% instead of using the ratio; percentages must be relative to CP.

Final Answer:
10%