By selling 33 meters of cloth a person gains the cost price of 11 meters. Find his gain % = ?

Answer: Option A

Let Selling price of 1 meters cloth = Rs. 1
Selling price of 33 meters cloth = Rs. 33
Cost price of 1 meter cloth = Rs. x
Cost price of 33 meters cloth = Rs. 33x
According to the question,
Profit = Selling price - Cost price
$$\begin{array}{rl}& \Rightarrow 11x=33-33x\\ & \Rightarrow 44x=33\\ & \Rightarrow x=\frac{33}{44}=\frac{3}{4}\\ & \text{Cost price of 1 metre}\\ & =\text{Rs}\text{.}\frac{3}{4}\\ & \text{Cost price of 33 metres}\\ & =\frac{3}{4}\times 33\\ & =\text{Rs}.\frac{99}{4}\end{array}$$
Selling price of 33 meters = Rs. 33
Profit = Selling price = Cost price
$$\begin{array}{rl}& =33-\frac{99}{4}\\ & =\frac{33}{4}\\ & \therefore \text{Profit }\%\\ & \text{ = }\frac{\frac{33}{4}}{\frac{99}{4}}\times 100\\ & =\frac{33}{99}\times 100\\ & =\frac{1}{3}\times 100\\ & =33\frac{1}{3}\%\end{array}$$

Alternate :
Let Selling price of 1 meters cloth = Rs. 1
Selling price of 33 meters cloth = Rs. 33
33 Selling price - 33 Cost price = 11 Cost price
33 Selling price = 44 Cost price
$$\begin{array}{rl}& \frac{\text{Selling price}}{\text{Cost price}}=\frac{4}{3}⟩1\\ & \text{Profit = 1}\\ & \text{Profit }\%=\frac{1}{3}\times 100\\ & =33\frac{1}{3}\%\end{array}$$