SOLUTION: What would be the formula for figuring out a percentage that as already been added to a total and you want to isolate the percentage already added? Example: $100 is the Total bi

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Question 814958: What would be the formula for figuring out a percentage that as already been added to a total and you want to isolate the percentage already added?
Example: $100 is the Total bill, taxes are included already (13%)
What was the original number (100) before taxes were added (13%)?
Thank You
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

 C + .13C = Total

 C(1+ .13)= Total

   C = Total%2F1.13+ If tax = 7.5%, for ex:  C = Total%2F1.075+

   C = 100%2F1.13= $88.50  (rounded to the nearest penny)