If loss is 1/3 of S.P., the loss percentage is -

Answer: Option C

$$\begin{array}{rl}& \text{Let S}\text{.P}\text{.}=\text{Rs}.x\\ & \text{Then,}\\ & \text{Loss}=\text{Rs}.\frac{x}{3}\\ & \text{C}\text{.P}\text{.}=\text{Rs}.\left(x+\frac{x}{3}\right)\\ & =\text{Rs}.\frac{4x}{3}\\ & \therefore \text{Loss }\%\\ & =\left(\frac{x}{3}\times \frac{3}{4x}\times 100\right)\%\\ & =25\%\end{array}$$