Percentage Discount given an Original Price of $400 and a Sale Price of $320

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 $400 and a Sale Price of $320 = 20%
Note: Reduction in Price = $400 – $320 = $80