A vendor bought toffees at 6 for a rupee. How many for a rupee must he sell to gain 20%?

Given Data

• Purchase rate = 6 toffees for Re. 1 ⇒ CP per toffee = Re. 1 ÷ 6 = Rs. 0.1667
• Target: 20% profit on CP

Step 1: Compute target SP per toffee
SP per toffee = CP × (1 + 20%) = (1/6) × 1.2 = 0.2 = Re. 1 ÷ 5

Step 2: Convert back to a convenient selling phrase
If SP per toffee is Re. 0.20, then he must sell 5 for Re. 1.

Checks & Common Pitfalls

• Profit is on cost price; multiply CP by 1.20 for a 20% gain.
• Do not invert the ratio; ensure the selling pack count decreases when seeking profit.

Final Answer
He should sell 5 for Re. 1 to gain 20%.