How do I write a formula to add the alternating cells in a column? It is a
rather large spreadsheet, so entering each cell individually would be rather
cumbersome and won't fit. Any insight would be greatly appreciated.

This formula will sum every other row A2, A4, A6, A8, A10:

=SUMPRODUCT(--(MOD(ROW(A2:A10)-ROW(A2),2)=0),A2:A10)

This formula will sum every other row A3, A5, A7, A9:

=SUMPRODUCT(--(MOD(ROW(A2:A10)-ROW(A2),2)=1),A2:A10)

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Biff
Microsoft Excel MVP


"Lissa" wrote in message
...
How do I write a formula to add the alternating cells in a column? It is
a
rather large spreadsheet, so entering each cell individually would be
rather
cumbersome and won't fit. Any insight would be greatly appreciated.

Found this online a while back...not sure where though:

Use these formulas when the data DOES start in row 1.
To start in row N, and sum rows N, 2N, 3N, etc, use
=SUM(IF(MOD(ROW($A$1:$A$20),$D$1)=0,$A$1:$A$20,0))


To start in row 1, and sum rows 1, 1+N, 1+(2N),etc use
=SUM(IF(MOD(ROW($A$1:$A$20)-1,$D$1)=0,$A$1:$A$20,0))

Maybe it came from he
http://www.ozgrid.com/Excel/sum-every-2nd-nth-cell.htm


Regards,
Ryan--


--
RyGuy


"Lissa" wrote:

How do I write a formula to add the alternating cells in a column? It is a
rather large spreadsheet, so entering each cell individually would be rather
cumbersome and won't fit. Any insight would be greatly appreciated.