# Excel - SUM Function Problem - Expert Solution

Question description:
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I need a formula for the sum of row a1-a500 where its a1*a2 + a3*4 + a5 * a6... etc
Solved by C. E. in 20 mins
This is the chat thread from the real Excelchat help session. It contains no private user information.
Excelchat Expert 30/05/2018 - 02:21
HI
User 30/05/2018 - 02:21
hello
Excelchat Expert 30/05/2018 - 02:21
Hope you are doing well today!
Excelchat Expert 30/05/2018 - 02:21
Welcome to got it pro!
User 30/05/2018 - 02:22
i just need a quick formula
User 30/05/2018 - 02:22
:)
Excelchat Expert 30/05/2018 - 02:22
OK
Excelchat Expert 30/05/2018 - 02:22
Excelchat Expert 30/05/2018 - 02:22
Pleases give me some time and see how it will work
Excelchat Expert 30/05/2018 - 02:22
1
User 30/05/2018 - 02:24
ill manually do an example on column g so u can see
Excelchat Expert 30/05/2018 - 02:24
Sure
Excelchat Expert 30/05/2018 - 02:25
Ok. I see
Excelchat Expert 30/05/2018 - 02:25
Is there certain math formula associate with this?
Excelchat Expert 30/05/2018 - 02:25
Or not really?
User 30/05/2018 - 02:25
no math formula
User 30/05/2018 - 02:25
just need a structure
User 30/05/2018 - 02:26
just need a formula for the cell number G8
Excelchat Expert 30/05/2018 - 02:26
Is there anyway, you can split the odd and even row into 2 seperate columns?
User 30/05/2018 - 02:26
so it calculates the sum of stuff before it
Excelchat Expert 30/05/2018 - 02:26
Sure. I see what you are trying to do
User 30/05/2018 - 02:26
ummm our current excel is daily columns, splitting into two would be a significant delay
User 30/05/2018 - 02:26
and lots of manual work
Excelchat Expert 30/05/2018 - 02:27
Yes. Thats true
User 30/05/2018 - 02:28
and we currently have over 2000 rows for each column
User 30/05/2018 - 02:28
so manually inputting a1*a2 + a3*a4 is going to take too long
Excelchat Expert 30/05/2018 - 02:28
Sure.
Excelchat Expert 30/05/2018 - 02:28
Please allow me couple of minutes to try something
Excelchat Expert 30/05/2018 - 02:29
Are you allow to split the column??
Excelchat Expert 30/05/2018 - 02:29
If yes, then there is a way to do it
Excelchat Expert 30/05/2018 - 02:29
=mod(A1,2)
User 30/05/2018 - 02:29
split columns?
Excelchat Expert 30/05/2018 - 02:29
For all the numbers in column A
Excelchat Expert 30/05/2018 - 02:30
we are calculating the reminder at this point
Excelchat Expert 30/05/2018 - 02:30
so, it will show either 1 or 0
User 30/05/2018 - 02:31
no i dont think we can split into two columns for now
Excelchat Expert 30/05/2018 - 02:32
Then, it may not possible to do so
User 30/05/2018 - 02:32
User 30/05/2018 - 02:32
for calculating only the odd numbered cells
User 30/05/2018 - 02:32
=ArrayFormula(SUM(IF(MOD(ROW(\$B\$2:\$B\$500),2)=0,\$B\$2:\$B\$500,0)))
User 30/05/2018 - 02:32
is there anyway to modify it
User 30/05/2018 - 02:33
so that its a1:a2, a3:a4 etc?
Excelchat Expert 30/05/2018 - 02:33
Please allow me to take a look
Excelchat Expert 30/05/2018 - 02:39
Well, I think this formula is good to use if you are not considering A1*A2+A3*A4+ etc.....
Excelchat Expert 30/05/2018 - 02:39
If you need very specific cell do multiply then do the sum, I think this formula may not work
Excelchat Expert 30/05/2018 - 02:40
Unless you allow to seperate 1 column into multiple, then this problem will be easier

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