A shopkeeper by selling 21 Nike shoes, earns a profit equal to the selling price of 5 Nike shoes. His profit percentage is

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

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

=> Selling price of 5 shoes = $$Rs. 5y$$

According to ques, => $$21(y - x) = 5y$$

=> $$21y - 21x = 5y$$

=> $$16y = 21x$$

=> $$\frac{x}{y} = \frac{16}{21}$$

Let Cost price, $$x = 16$$ and selling price, $$y = 21$$

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

= $$\frac{21 - 16}{16} \times 100$$

= $$\frac{125}{4} = 31.25\%$$

=> Ans - (A)