If the price of a book is first decreased by 25% and then increased by 20%, then the net charges in the price will be :

Answer: Option D

Let the original price be Rs. 100
New final price :
= 120% of (75% of Rs. 100)
= Rs. $$\left(\frac{120}{100}\times \frac{75}{100}\times 100\right)$$
= Rs. 90
∴ Decrease = 10%