Question

A number first increases by 20% and then decreases by 20%. Find the percentage
increase or decrease on the whole.
​

Answer 1

Let the number be 100

In 1st condition,

Increase = 20% of 100

= 20/100 × 100

= 20

∴ Number after this increase = 100 + 20

= 120

In 2nd condition,

Decrease = 20% of 120

= 20/100 × 120

= 24

∴ Number after this decrease = 120 – 24 = 96

⇒ Total decrease on the whole = 24 – 20 = 4

And the percentage decrease on the whole = 4/100 × 100

= 4%