Percentage Discount given an Original Price of $1,278 and a Sale Price of $1,150.20

Discount Rate = 1 –  
Discount Rate = 1 – 0.9
Discount Rate = 0.1
0.1 Converted to a Percent: 0.1 = 10%
Percentage Discount given an Original Price of $1,278 and a Sale Price of $1,150.20 = 10%
Note: Reduction in Price = $1,278 – $1,150.20 = $127.80