When CP of 20 equals SP of 15 — compute profit percentage If the cost price of 20 articles equals the selling price of 15 articles (same type), find the profit percentage.

Introduction / Context:
Total cost equaling total revenue for different counts reveals the SP/CP ratio per unit. This directly gives profit percentage without needing explicit rupee values.

Given Data / Assumptions:

• 20 * CP per unit = 15 * SP per unit.
• Identical items with uniform unit prices.

Concept / Approach:
From 20C = 15S ⇒ S/C = 20/15 = 4/3. Profit% = (S − C)/C * 100 = (4/3 − 1)*100 = 1/3*100.

Step-by-Step Solution:
S/C = 4/3.Profit fraction = 1/3.Profit% = 33 1/3 %.

Verification / Alternative check:
Let C = ₹3 ⇒ S = ₹4. Then 20C = ₹60 and 15S = ₹60 (consistent). Profit per unit = ₹1 on ₹3 ⇒ 33 1/3%.

Why Other Options Are Wrong:
33 1/2%, 33 1/5%, 33 1/7% and 25% do not match the exact 4/3 ratio.

Common Pitfalls:
Inverting the ratio to 3/4 or claiming loss instead of profit.

Final Answer:
33 1/3 %