Question

7. 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 = \frac{20}{100}\times100=20

100

20

×100=20

∴ Number after this increase = 100 + 20 = 120

In 2nd condition

Decrease = 20% of 120 = \frac{20}{100}\times120=24

100

20

×120=24

∴ Number after this decrease = 120 - 24 = 96

> Total decrease on the whole = 24 -20 = 4

And the percentage decrease on the whole = \frac{4}{100}\times100=4\%

100

4

×100=4%