Buy–sell comparison on count and unit price A man buys 10 articles for Rs 8 and sells each for Rs 1.25. What is his gain percentage?

Introduction / Context:
Here we compare per-unit cost and per-unit selling price. Converting the bulk purchase into a unit cost is the first step, followed by computing gain% on cost price.

Given Data / Assumptions:

• 10 articles cost Rs 8 ⇒ CP per article = Rs 0.80.
• SP per article = Rs 1.25.

Concept / Approach:
Gain per article = SP - CP. Gain % = (Gain / CP) * 100.

Step-by-Step Solution:
CP per article = 8 / 10 = 0.80.Gain per article = 1.25 - 0.80 = 0.45.Gain % = (0.45 / 0.80) * 100 = 56.25% = 56 1/4%.

Verification / Alternative check:
On 10 items: total CP = 8, total SP = 12.5, total gain = 4.5; gain% = (4.5/8)*100 = 56.25% (same).

Why Other Options Are Wrong:
20% and 50% underestimate; 37 1/2% is incorrect; 62 1/2% overestimates the gain.

Common Pitfalls:
Using SP as the base for percentage or misreading '10 for Rs 8' as '8 for Rs 10'.

Final Answer:
56 1/4%