The ratio of the cost price and selling price is 5 : 4, the loss percent is = ?

Answer: Option A

According to question,
$$\begin{array}{rl}& \frac{\text{Cost price}}{\text{Selling price}}=\frac{5}{4}\}\text{1 unit loss}\\ & \text{loss}\%=\frac{1}{5}\\ & =20\%\text{ loss}\end{array}$$