Percentage Discount given an Original Price of $40 and a Sale Price of $30

Discount Rate = 1 –  
Discount Rate = 1 – 0.75
Discount Rate = 0.25
0.25 Converted to a Percent: 0.25 = 25%
Percentage Discount given an Original Price of $40 and a Sale Price of $30 = 25%
Note: Reduction in Price = $40 – $30 = $10