Let’s start by understanding what we know: The vendor buys 6 toffees for 1 rupee. This means that each toffee costs 1/6 of a rupee.

To find out how many toffees he should sell for a rupee to make a 20% profit, we need to:

1. Calculate the cost of each toffee
2. Add 20% to get the selling price
3. Convert this into toffees per rupee

Let’s calculate: Cost per toffee = 1/6 rupee

To make a 20% profit, the selling price should be: Selling price = Cost + 20% of Cost Selling price = Cost × (1 + 20/100) Selling price = Cost × 1.2 Selling price per toffee = (1/6) × 1.2 Selling price per toffee = 1/5 rupee

Now, if each toffee sells for 1/5 of a rupee, then for one rupee, the vendor should sell: Number of toffees = 1 ÷ (1/5) = 5 toffees

Therefore, the vendor must sell 5 toffees for a rupee to gain a 20% profit.

To verify this makes sense:

• Cost of 5 toffees = 5 × (1/6) = 5/6 rupee
• Selling price = 1 rupee
• Profit = 1 – 5/6 = 1/6 rupee
• Profit percentage = (1/6 ÷ 5/6) × 100 = 20%

This problem illustrates an important principle in retail pricing: when you want to achieve a certain profit margin, you need to adjust your selling quantity accordingly. The vendor started with buying 6 toffees for a rupee but needs to sell 5 toffees for a rupee to make his desired profit. This reduction in quantity for the same price allows him to cover his costs and make his target profit margin.