This should be simple?

[Jim Brass]

If you have a column of numbers and want to add every third one, what
formula do you use?
I tried stuff like
=SUMIF(A3:A13,MOD(ROW(),3)=0) as an array formula

My mind is drawing a blank. Thanks Jim

 

[Bob Phillips]

=SUMPRODUCT(A3:A13,--(MOD(ROW(A3:A13),3)=0))

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HTH

RP
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