A person calculates `25%` loss at S.P. find his loss at C.P.

Answer

To solve the problem of finding the loss percentage at the cost price (C.P.) when a person calculates a 25% loss at the selling price (S.P.), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Loss Percentage**:
The person calculates a 25% loss at the selling price. This means that the selling price is 75% of the cost price because a loss of 25% implies that 100% - 25% = 75%.

**Hint**: Remember that a loss of X% means you are left with (100 - X)% of the cost price.

2. **Setting Up the Relationship**:
Let the cost price (C.P.) be represented as 100 units (for simplicity). Therefore, the selling price (S.P.) can be calculated as:
\[ S.P. = 75\% \text{ of C.P.} = 75\% \text{ of } 100 = 75 \text{ units} \]

**Hint**: When you set the cost price to 100 units, it makes percentage calculations easier.

3. **Calculating the Loss**:
The loss incurred can be calculated as:
\[ \text{Loss} = \text{C.P.} - \text{S.P.} = 100 - 75 = 25 \text{ units} \]

**Hint**: Loss is always calculated as the difference between cost price and selling price.

4. **Finding the Loss Percentage at C.P.**:
The loss percentage can be calculated using the formula:
\[ \text{Loss Percentage} = \left( \frac{\text{Loss}}{\text{C.P.}} \right) \times 100 \]
Substituting the values we have:
\[ \text{Loss Percentage} = \left( \frac{25}{100} \right) \times 100 = 25\% \]

**Hint**: The loss percentage is always calculated based on the cost price.

### Final Answer:
The loss percentage at the cost price (C.P.) is **25%**.