Formula needed for adding every nth column on another sheet

[JJ]

Hi

I have tried everything I can think of but with no luck - can somebody
please help.

On sheet 2 I have all the data in columns from rows 1-20.

On sheet 1 I want the total of the sums of every 3rd column.

ie. Sheet 1: A1 = sum Sheet 2: A1:A20
Sheet 1: B1 = sum Sheet 2: D120
Sheet 1: C1 = sum Sheet 2: G1:G20 and so on...

Instead of manually entering all the formulas on Sheet 1 for the sum totals
of every 3rd column, is there a formula I can enter in A1 on Sheet 1 and copy
across the row?

Thanks for any help!!

 

[RagDyer]

Try this:

=SUM(INDEX(Sheet2!$A1:$AB20,1,COLUMNS($A:A)*3-2):INDEX(Sheet2!$A1:$AB20,20,COLUMNS($A:A)*3-2))

You can enter this *anywhere*, and copy across as needed, though I've only
sized this out to Column AB!

 

[JJ]

Thanks RagDyer, it worked a treat!! I would never have got that myself.

 

[Teethless mama]

Shorter version:

=SUM(INDEX(Sheet2!$1:$20,,COLUMNS($A:A)*3-2))

 

[RagDyeR]

Nice!

I've noticed that you DO have a fine comprehension of that Index()
function!<g>

 

[RagDyeR]

You're welcome, and appreciate the feed-back, but do check out Tm's shorter
formula.

 

[Bob Umlas]

Sheet1!A1:
=SUM(OFFSET(Sheet2!$A$1,0,(COLUMN()-1)*3,20,1)) and fill right

Bob Umlas
Excel MVP