A shopkeeper by selling 20 Timex watches, earns a profit equal to the selling price of 4 Timex watches. His profit percentage is

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

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

=> Selling price of 4 watches = $$Rs. 4y$$

According to ques, => $$20(y - x) = 4y$$

=> $$20y - 20x = 4y$$

=> $$16y = 20x$$

=> $$\frac{x}{y} = \frac{16}{20} = \frac{4}{5}$$

Let Cost price, $$x = 4$$ and selling price, $$y = 5$$

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

= $$\frac{5 - 4}{4} \times 100$$

= $$\frac{100}{4} = 25\%$$

=> Ans - (B)