Cost build for a cup of coffee — Coffee powder packet costs ₹ 20 and makes 10 cups. Milk costs ₹ 30 per litre; each cup uses 200 ml. If the seller targets a 25% profit on total cost, what should be the selling price per cup?

Introduction / Context: This kitchen arithmetic problem combines a fixed-quantity ingredient (the coffee packet) and a variable ingredient (milk per cup). We compute the total cost for 10 cups, apply the desired profit, and divide by cups to get the per-cup selling price.

Given Data / Assumptions:

• Coffee packet = ₹ 20 and yields 10 cups ⇒ coffee cost per cup = ₹ 2.
• Milk = ₹ 30/litre = ₹ 0.03/ml.
• Milk per cup = 200 ml ⇒ milk cost per cup = 200 * 0.03 = ₹ 6.
• Total cups = 10.

Concept / Approach: Total cost for 10 cups = coffee packet cost + milk cost for 10 cups. Apply 25% profit on this total to get required total revenue; then divide by 10.

Step-by-Step Solution:

Verification / Alternative check: Per cup cost = ₹ 8; adding 25% gives ₹ 10, exactly matching the result.

Why Other Options Are Wrong: ₹ 12.50 overshoots 25%; ₹ 6.25 and ₹ 8 ignore profit; ₹ 9.50 underprices the target margin.

Common Pitfalls: Forgetting to convert millilitres to litres for milk pricing, or splitting the coffee packet cost incorrectly across cups.

Final Answer: ₹ 10