A shopkeeper bought pens at the rate of ₹1,350 for 15 dozen pens and sold them at the rate of ₹495 for 5 dozen pens. His percentage profit or percentage loss is :

Profit 10%

Cost price of 15 dozen pens = 1350

One dozen = 12 quantities

Cost price of a pen = \(\frac{1350}{13 × 12}\) = 7.5

Selling price of a pen = \(\frac{495}{4 × 12 }\) = 8.25

Profit % = \(\frac{(8.25 - 7.5)}{7.5}\) × 100 = 10%