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 ?

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