If the price of erasers goes down by 25%, a man can buy 2 more erasers for a rupee. How many erasers are available for a rupee ?

Answer: Option C

Let the original price of an eraser be Rs. x
Reduced price = 75% of Rs. x = Rs. $$\frac{3x}{4}$$
$$\begin{array}{rl}& \therefore \frac{1}{\left(\frac{3x}{4}\right)}-x=2\\ & \Rightarrow \frac{4}{3x}-\frac{1}{x}=2\\ & \Rightarrow \frac{1}{3x}=2\\ & \Rightarrow 6x=1\\ & \Rightarrow x=\frac{1}{6}\end{array}$$
Hence, number of erasers available for a rupee = 6