With Units in column A and Pieces-together in B, I used
=SUMPRODUCT(B2:B4,A2:A4/B2:B4)/SUMPRODUCT(A2:A4/B2:B4)
to get a value of 1.23 for your data set.
I find it useful to solve a problem using a data set that lets me do the
math in my head.
Try solving:
10 units packed 2 to a box
6 units packed 1 to a box
4 units packed 4 to a box
Now list the contents of each box:
2,2,2,2,2,1,1,1,1,1,1,4 with an average of 1.67
Now try my formula - it seems to work!
NOTE: to expand the problem use something like
=SUMPRODUCT(B2:B1001,A2:A4/B2:B1001)/SUMPRODUCT(A2:A1001/B2:B1001)
but not
=SUMPRODUCT(B:B,A:A/B:B)/SUMPRODUCT(A:A/B:B) as SUMPRODUCT (or any array
function) will not work with references to a complete column.
best wishes

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Bernard V Liengme
www.stfx.ca/people/bliengme
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> I am trying to weight out the average number of peices packed together
> per purchase order to end up with an average of pieces packed together
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>
> Thanks!