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Math Stumper

Bright01
Bright01 asked
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Last Modified: 2016-08-24
EE Pros (and Math Wizards),

I have a program that calculates the difference between a "BEFORE" and an "AFTER" number and represents it as a % Change.  It works great when both numbers are positive.  BUT.... if the BEFORE value is negative and the AFTER value is positive, it does not calculate the result correctly.  Either my formula is wrong or I'm dealing with an anomaly in math......... ;-(

See Attached WS/file.

Thank you in advance!  


B.
Measuring-a-Change.xls
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d-glitchResearch Engineer - Electrical
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Commented:
I believe your program is correct.
You will get odd looking results when the before and after change sign.
d-glitchResearch Engineer - Electrical
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Commented:
-1  to +2  is a change of -300%

The -1 represents 100% of the original value.
A change of +3 is  -3*-1 or 300% of the original value.
IanStatistician
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Commented:
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Commented:
Thanks ShannonEE and d-glitch for jumping in here.  

Here's my problem.  The math may be correct, but it flies in the face of logic.  When I have a negative number and turn it positive, logically "it's an improvement".  So the growth, or change should be positive.  But mathematically, it's not.

Say for example, the CURRENT number represents a loss of -3% and the FUTURE is a gain of +2%. That's a difference of +5%.  Is there a way to solve for the difference between the math and the logic in situations where you start with a negative number and move into a positive direction to produce a positive improvement to the change?

Is this logic vs. math?  I'm surprised there is a difference..........

B.
Manager; IT Consultant
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Commented:
Alexandre,  I used your formula.  You nailed what I was trying to do in addition to answering the question from a math perspective.  ShannonEE, thanks also for your commentary to help me better understand the situation.

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