If the cost price is 90% of the selling price, what is the profit percent ?

Answer: Option D

According to the question,
$$\begin{array}{rl}& \text{C}\text{.P}\text{. = }\frac{90}{100}\text{S}\text{.P}\text{.}\\ & \frac{\text{C}\text{.P}\text{.}}{\text{S}\text{.P}\text{.}}\text{ = }\frac{9}{10}⟩\text{1 unit profit}\\ & \text{Profit }\%=\frac{1}{9}\times 100\\ & =11\frac{1}{9}\%\end{array}$$