The cost price of 10 articles is equal to the selling price of 9 articles. Find the profit percent.

Answer

To solve the question, "The cost price of 10 articles is equal to the selling price of 9 articles. Find the profit percent," we can follow these steps:

### Step-by-Step Solution:

1. **Define the Cost Price (CP) of One Article:**
Let the cost price of one article be \( x \).

2. **Calculate the Cost Price of 10 Articles:**
The cost price of 10 articles is:
\[ \text{CP of 10 articles} = 10 \times x = 10x \]

3. **Define the Selling Price (SP) of One Article:**
According to the problem, the cost price of 10 articles is equal to the selling price of 9 articles. Therefore, we can express the selling price of 9 articles as:
\[ \text{SP of 9 articles} = 10x \]

4. **Calculate the Selling Price of One Article:**
The selling price of one article can be calculated as:
\[ \text{SP of 1 article} = \frac{\text{SP of 9 articles}}{9} = \frac{10x}{9} \]

5. **Calculate the Profit:**
Profit is calculated using the formula:
\[ \text{Profit} = \text{SP} - \text{CP} \]
For 1 article, the profit is:
\[ \text{Profit} = \frac{10x}{9} - x \]
To simplify this, we can find a common denominator:
\[ \text{Profit} = \frac{10x}{9} - \frac{9x}{9} = \frac{10x - 9x}{9} = \frac{x}{9} \]

6. **Calculate the Profit Percentage:**
The profit percentage is given by the formula:
\[ \text{Profit Percentage} = \left(\frac{\text{Profit}}{\text{CP}}\right) \times 100 \]
Substituting the values we have:
\[ \text{Profit Percentage} = \left(\frac{\frac{x}{9}}{x}\right) \times 100 \]
The \( x \) in the numerator and denominator cancels out:
\[ \text{Profit Percentage} = \left(\frac{1}{9}\right) \times 100 = \frac{100}{9} \]

7. **Convert to Mixed Fraction:**
The profit percentage can be expressed as:
\[ \frac{100}{9} \approx 11 \frac{1}{9} \% \]

### Final Answer:
The profit percentage is \( 11 \frac{1}{9} \% \).