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Old 11-01-2018, 07:35 PM   #19
franken
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Join Date: Jun 2013
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Posts: 3,053
Re: Payback calculator for upgrade vs MPG

Apparently you missed the obvious flaws pointed out in the original equation that were pointed out. You can't divide by a value that doesn't exist, and you can't use the cell that contains the formula in the formula. I was talking about the units in my version, not the original. Also, doing an inversion in the equation simply places the values in the numerator, so why not put them there in the first place.

Anyone can use both formulas and see what happens w/ simple numbers...

Quote:
Originally Posted by huntznsam View Post
Ignore this if you aren't a math geek.

Franken,
Units work as written - I think you missed the inverse. 1 over m/g=g/m so the units work out as $ over ($/g*g/m). The $ cancel, the g cancel, and you are left with miles. Been a million years since I did that in school.

We start with the basic formula and work from there. Miles per year/MPG=gallons per year. GPY*dollars per gallon=gas cost per year.

You can check by using B11*B8 and B12*B8 in my sheet to get cost of gas before and after. The difference is the cost of conversion, B2.
Huntz
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