Target profit via units per rupee: A man buys toffees at 6 for ₹ 1. To earn a profit of 50%, how many toffees should he sell for ₹ 1?

Introduction / Context:
When buying and selling are expressed as “units per rupee,” convert to per-unit costs and prices. Then enforce the desired profit percentage to find the corresponding selling rate.

Given Data / Assumptions:

• Cost rate: 6 for ₹ 1 ⇒ CP per toffee = ₹ 1/6.
• Desired profit = 50%.

Concept / Approach:
SP per toffee must be CP * 1.5. Convert this SP per toffee back to “toffees per ₹ 1.”

Step-by-Step Solution:
Target SP per toffee = (1/6) * 1.5 = 1/4 rupeeHence, toffees per ₹ 1 at SP = 1 ÷ (1/4) = 4

Verification / Alternative check:
Buying 6 for ₹ 1 and selling 4 for ₹ 1 implies revenue per 6 pieces is 6 * (1/4) = ₹ 1.5, a 50% profit on ₹ 1 cost.

Why Other Options Are Wrong:

• 5 / 2 / 6: do not produce 50% profit when reconciled with CP = 1/6 per piece.

Common Pitfalls:

• Averaging unit counts instead of converting to per-unit monetary values.

Final Answer:
4