If the selling price of 10 pens is equal to the cost price 14 pens, find the gain percent.

Explanation

To solve the problem, we need to find the gain percent based on the information given about the selling price and cost price of the pens.

### Step-by-Step Solution:

1. **Define Variables**:
Let the cost price (CP) of 1 pen be \( x \) rupees.
Let the selling price (SP) of 1 pen be \( y \) rupees.

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