I have opened up a worksheet that a coworker created last year and cannot
figure out the purpose of the isnumber function in this formula:
{=SUM(N27:N117*P27:P117)/SUM(N27:N117*ISNUMBER(P27:P117))}.

I have looked it up in Excel help and on Google with little insight. If
anyone can please tell me what the purpose of this function is/does, it will
be greatly appreciated. The data it is pulling from is all numbers.

Regards,

Jon