A trader marked the selling price of an article at 10% above the cost price. At the time of selling he allows certain discount and suffers a loss of 1%. He allowed the discount of ?

Answer: Option B

Let the cost price of an article = Rs. 100
Marked price of an article = Rs. 110 (10% above)
Selling price of an article = Rs. 99 (10% discount)
$$\begin{array}{rl}& \text{Difference}=110-99\\ & \text{ = Rs}\text{. 11}\\ & \text{Discount}=\frac{11}{110}\times 100\\ & =10\%\end{array}$$