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Why do you have a minus 1 at the end?<br />
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Should the -1 be part of the denominator? &nbsp;If so, should it be: &nbsp;<br />
=IF(ISERROR((D18+D19)/D20)<wbr />,&quot;&quot;,(D18+D<wbr />19)/(D20-1<wbr />))<br />
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Not sure what you mean by &quot;inconsistent&quot;
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Why do you have a minus 1 at the end?

Should the -1 be part of the denominator?  If so, should it be:  
=IF(ISERROR((D18+D19)/D20),"",(D18+D19)/(D20-1))

Not sure what you mean by "inconsistent"

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Why would I get an inconsistent formula on <br />
<br />
=IF(ISERROR((D18+D19)/D20)<wbr />,&quot;&quot;,(D18+D<wbr />19)/D20-1)<wbr />
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Why would I get an inconsistent formula on 

=IF(ISERROR((D18+D19)/D20),"",(D18+D19)/D20-1)

Inconsistant formula

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