A trader allows a trade discount of 20% and a cash discount of 61/4\% on the marked price of the goods and gets a net gain of 20% of the cost. By how much above the cost should the goods be marked for the sale = ?

Answer: Option C

$$\begin{array}{rl}& \text{Single equivalent discount }\\ & =\left(20+\frac{25}{4}-\frac{20\times 25}{400}\right)\%\\ & =25\%\end{array}$$
Let cost price of article = Rs. 100
∴ Selling price of article = Rs. 120 (20% profit)
Let the marked price of article = Rs. x
$$\begin{array}{rl}& \therefore x\times \frac{75}{100}=120\\ & \Rightarrow x=\frac{120\times 100}{75}\\ & \Rightarrow x=\text{Rs}\text{. 160}\\ & \text{Required percentage }\\ & \text{ = }\frac{160-100}{100}\times 100\\ & =60\%\end{array}$$