Sum Problems

[tslayer]

I have a column and I want to add every third cell totaling 36 cells. Excel gives me an error when I select more than 30 individual cells. Any help would be appreciated

Thanks

tslayer

[Dav]

Perhaps something like the following

=SUMPRODUCT((A3:A92)*(MOD(ROW(A3:A92),3)=1))

you may need to change the range you wish to sum eg a3:a92, and the =1 bit may be =0 or =2 depending which cells you wish to sum

Regards

Dav

[arthurbr]

Some ideas here :
http://www.cpearson.com/excel/excelF.htm#SumEveryNth
Beware, they are array formulas !

[tslayer]

Thanks For Replying.

Just getting back to this. Cannot get this to work. I have attached a file.

I need to add cell C10, C14, C18 and so on... 36 cells total.

I will then need to do the same for C11, C15, C19 etc..

Thanks again, excellent forum.

Tslayer

[davesexcel]

you zipped a word doc, why not zip an xl workbook??

[Paul]

Try these formulas:

To count cells A10, A14, A18, etc. for 36 entries use:
=SUM(IF(MOD(ROW($A10:$A150)-2,4)=0,$A10:$A150,0))

To count cells A11, A15, A19, etc. for 36 entries use:
=SUM(IF(MOD(ROW($A11:$A151)-3,4)=0,$A11:$A151,0))

To count cells A12, A16, A20, etc. for 36 entries use:
=SUM(IF(MOD(ROW($A12:$A152),4)=0,$A12:$A152,0))

To count cells A13, A17, A21, etc. for 36 entries use:
=SUM(IF(MOD(ROW($A13:$A153)-1,4)=0,$A13:$A153,0))

** These are all ARRAY formulas. After typing these formulas in you must press CTRL+SHIFT+ENTER to make them work, not just ENTER. **