A number is increased by 20% and then decreased by 20%, the final value of the number is ?

Here, x = 20 and y = - 20
Therefore, the net % change in value
= $x + y + \frac{xy}{100}$ %
=  $20 + -20 + \frac{20 \times -20}{100}$%  or  - 4%

Since the sign is negative, there is a decrease in value by 4%.