This maybe a strange question, but I have a SUMPRODUCT function that
works in Excel, however, I don't understand why it does.

Here is what I have:

An array of task times (Duration) B3:B41

A matrix of names of people assigned to the various tasks throughout the
week (WEEK)D3:H41 (The names appear one or more times)

The array of individual names appears in A43:A61

Now I want to know the total time each individual spends carrying out
one or more of the tasks. This is done with:

SUMPRODUCT((WEEK=$A43) * Duration)

This function appears beside each name with the row number incremented
accordingly. IT WORKS!

Here is my problem, I can't find anywhere in the documentation for this
function (or another example) where a row number in a matrix will look
up the corresponding row number in an array. So I don't understand why
it provides the desired result.

I would appreciate more examples of this use of SUMPRODUCT and technical
explanation of why it works.

TIA



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Regards,
Vic Chapman