Question

I have two table with figures with dimension 9*9. I would like to compute

sum(aij*bij) over j

with obvious notation with one formula only.

For now, I am first computing a 9*9 table filled with aij*bij in each cell, and then in a new column I am doing a sum over columns of values in this 9*9 table. It is two step. I would like to do that in one step to save space and time.

What is syntax ?

Thanks

Answer 1

Another approach here – use array SUM formula: =SUM(A1:I1*K1:S1). However, as you type it into cell, press CTRL+SHIFT+ENTER instead of usual ENTER. As a result, this formula will be displayed as {=SUM(A1:I1*K1:S1)} – brackets indicate that this is an array formula. However, they should NOT be manually added.

@chuff answer is absolutely correct and I upvoted it, but using array formulas has at least 1 advantage: with them you may do much more magic tricks which are not / hardly implemented using SUMPRODUCT or any similar functions.

Please also see Remark section there: http://office.microsoft.com/en-001/excel-help/sumproduct-HP005209293.aspx

Use this sample file as a demo for both solutions: https://www.dropbox.com/s/0xr8iif920uqpqf/SUMPRODUCT.xlsx

Choose any solution which is more suitable for you! (: