Percentage Discount given an Original Price of $9 and a Sale Price of $4.50

Discount Rate = 1 –  
Discount Rate = 1 – 0.5
Discount Rate = 0.5
0.5 Converted to a Percent: 0.5 = 50%
Percentage Discount given an Original Price of $9 and a Sale Price of $4.50 = 50%
Note: Reduction in Price = $9 – $4.50 = $4.50