A fan listed at Rs. 150 with a discount of 20%. What additional discount must be offered to the customer to bring the net price to Rs. 108 ?

Answer: Option D

Selling price after given 20% discount
$$\begin{array}{rl}& =150\times \frac{\left(100-20\right)}{100}\\ & =120\\ & \text{So,}\\ & \Rightarrow 120\times \frac{x}{100}=108\\ & \Rightarrow x=90\end{array}$$
∴ Required additional discount = (100 - 90)% = 10%