Let's say - hypothetically speaking - a sales man tells you: You will get X% off of the list price!. How is that calculated correctly? I am asking this question in the most unbiased possible way by giving you three examples where I am using $100 as the list price. Is the correct method A or is it B?

10% off: Almost no difference
Discount methods, 10% discount.PNG

30% off: Now we are starting to see a difference
Discount methods, 30% discount.PNG

99% off: HUGE difference.
Discount methods, 99% discount.PNG

So what method is correct? A or B?