Final answer:
The merchant made a profit of approximately 11.76% by buying pens at 8 for ₹34 and selling them at 12 for ₹57.
Step-by-step explanation:
The student has asked to calculate the profit percent of a merchant who bought and sold pens. Initially, pens were bought at the rate of 8 for ₹34 (cost price), and later sold at the rate of 12 for ₹57 (selling price).
To find the profit percent, we first determine the cost price and selling price for one pen.
The cost price for one pen is ₹34 divided by 8, which is ₹4.25.
The selling price for one pen is ₹57 divided by 12, which is ₹4.75.
The profit per pen is the selling price minus the cost price, which amounts to ₹4.75 - ₹4.25 = ₹0.5 per pen.
The profit percentage is then calculated by dividing the profit per pen by the cost price per pen and multiplying by 100, resulting in (0.5 / 4.25) × 100, which gives us a profit percent of approximately 11.76%.