A shopkeeper by selling 13 Titan watches, earns a profit equal to the selling price of 3 Titan watches. His profit percentage is

Let cost price of a watch = $$Rs. x$$

Selling price of a watch = $$Rs. y$$

=> Selling price of 3 watches = $$Rs. 3y$$

According to ques, => $$13(y - x) = 3y$$

=> $$13y - 13x = 3y$$

=> $$10y = 13x$$

=> $$\frac{x}{y} = \frac{10}{13}$$

Let Cost price, $$x = 10$$ and selling price, $$y = 13$$

$$\therefore$$ Profit % = $$\frac{y - x}{x} \times 100$$

= $$\frac{13 - 10}{10} \times 100$$

= $$3 \times 10 = 30\%$$

=> Ans - (A)