Percentage Discount given an Original Price of $500 and a Sale Price of $400

Discount Rate = 1 –  
Discount Rate = 1 – 0.8
Discount Rate = 0.2
0.2 Converted to a Percent: 0.2 = 20%
Percentage Discount given an Original Price of $500 and a Sale Price of $400 = 20%
Note: Reduction in Price = $500 – $400 = $100