A number is decreased from 125 to 100; find the percentage decrease.

Given:

Initial Number = 125

Final Number = 100

Decrease in number = Initial number - Final number

Decrease in number = 125 - 100 = 25

Percentage decrease = $\dfrac{\text{Decrease in number}}{\text{Initial Number}} \times 100$ %

= $\dfrac{25}{125} \times 100$ %

= $\dfrac{2,500}{125}$ %

= 20%

The percentage decrease = 20%.