Short Answer 
The shopkeeper must sell 2500 toffees to earn a profit of ‚Çπ125, calculated by determining the cost price per toffee as 0.2 rupees and the selling price as 0.25 rupees, resulting in a profit of 0.05 rupees per toffee.
Step 1: Calculate Cost Price per Toffee
To determine the cost price (CP) per toffee, we first note the shopkeeper buys 5 toffees for 1 rupee. This can be calculated as:
- CP per toffee = 1 rupee / 5 toffees = 0.2 rupees
Step 2: Calculate Selling Price per Toffee
The next step is to find the selling price (SP) per toffee. The shopkeeper sells 4 toffees for 1 rupee, which gives us:
- SP per toffee = 1 rupee / 4 toffees = 0.25 rupees
Step 3: Calculate Total Toffees Needed for Profit
Now, we need to find out how many toffees must be sold to achieve a profit of ‚Çπ125. First, we calculate the profit per toffee:
- Profit per toffee = SP – CP = 0.25 – 0.2 = 0.05 rupees
- To find the number of toffees, use the formula: Number of Toffees = Total Desired Profit / Profit per Toffee
- Substituting values gives: Number of Toffees = 125 / 0.05 = 2500
Thus, the shopkeeper must sell 2500 toffees to earn a profit of ‚Çπ125.