Question

A number is increased by 20% and the increased number is decreased by 20%. Find the
net increase or decrease percent.

Answer 1

Let the number = x

So, we have to find x increased by 20% and then decreased by 20% and the  net increase or decrease percent.

So, the increase by 20% =  x + (20/100)x

= x + (1/5)x = x + (1x/5)

= 5x/5 + 1x/5

= 6x/5

Now, the decrease by 20% = 6x/5 - 6x/5 * 20/100

= 6x/5 - 6x/5 * 1/5

=6x/5 - 6x/25

=30x/25 - 6x/25

= 24x/25

Now the net decrease = x - 24x/25

= 25x/25 - 24x/25

= x/25

Decrease percentage = (Net decrease/ Original number × 100)%

= ((x/25)/x)*100 %

= (x/25 * 1/x) * 100 %

= 1/25 * 100 %     [As we can cancel the x in the numerator and the x in the denominator]

= 100/25 %

= 4%

Hope this helps you!