Percentage Discount given an Original Price of $40 and a Sale Price of $25

Discount Rate = 1 –  
Discount Rate = 1 – 0.625
Discount Rate = 0.375
0.375 Converted to a Percent: 0.375 = 37.5%
Percentage Discount given an Original Price of $40 and a Sale Price of $25 = 37.5%
Note: Reduction in Price = $40 – $25 = $15