Gain is reckoned on the selling price.

Answer

To solve the question "Gain is reckoned on the selling price," let's break it down step by step.

### Step 1: Understand the Terms
- **Gain (Profit)**: The difference between the selling price and the cost price.
- **Selling Price (SP)**: The price at which the product is sold.
- **Cost Price (CP)**: The price at which the product was purchased.

### Step 2: Identify the Given Values
Suppose:
- Cost Price (CP) = 8 rupees
- Selling Price (SP) = 10 rupees

### Step 3: Calculate the Gain (Profit)
To find the gain, we use the formula:
\[ \text{Gain} = \text{Selling Price} - \text{Cost Price} \]
Substituting the values:
\[ \text{Gain} = 10 \, \text{rupees} - 8 \, \text{rupees} \]
\[ \text{Gain} = 2 \, \text{rupees} \]

### Step 4: Calculate Gain Percentage
To express the gain as a percentage of the selling price, we use the formula:
\[ \text{Gain Percentage} = \left( \frac{\text{Gain}}{\text{Selling Price}} \right) \times 100 \]
Substituting the values:
\[ \text{Gain Percentage} = \left( \frac{2 \, \text{rupees}}{10 \, \text{rupees}} \right) \times 100 \]
\[ \text{Gain Percentage} = 0.2 \times 100 \]
\[ \text{Gain Percentage} = 20\% \]

### Final Answer
The gain is 2 rupees, and the gain percentage based on the selling price is 20%.

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