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Calculate percentage saved between two numbers?

I have two numbers, the first, is the original price, the second, is the discounted price.

I need to work out what percentage a user saves if they purchase at the second price. 

example
25, 10 = 60%  
365, 165 = 55%

What I dont know is the formula to calculate this.

Solution

  • I know this is fairly old but I figured this was as good as any to put this. I found a post from yahoo with a good explanation:

    Let's say you have two numbers, 40 and 30.  

  30/40*100 = 75.
  So 30 is 75% of 40.  

  40/30*100 = 133. 
  So 40 is 133% of 30. 

The percentage increase from 30 to 40 is:  
  (40-30)/30 * 100 = 33%  

The percentage decrease from 40 to 30 is:
  (40-30)/40 * 100 = 25%. 

These calculations hold true whatever your two numbers.

    Original Post