# Normal v Array formulae

#### tiredofit

##### Well-known Member
On my worksheet, cells A1 through to B6, I have the values 1,2,3,4,5,6 from A1, A2, A3, etc.

In cell D1, I type:

Rich (BB code):
``[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]=SUM(A1:A3*B1:B3)``
and enter it as an ARRAY formula to get the result of:

Rich (BB code):
``32``
I understand how this is arrived. It is multiplying cell A1 with B1, then A2 with B2 and then A3 with B3, then summing it, ie 4+10+18=32.

However in cell D2, if I typed:

Rich (BB code):
``=SUM(A1:A3*B1:B3)​``

but this time I enter it as a NORMAL formula, I get the result of:

Rich (BB code):
``10``
What exactly is Excel doing to get the value of 10?

Thanks

[/FONT]

#### Fluff

##### MrExcel MVP, Moderator
It's multiplying 2*5, ie the values in A1:B6 that are on the same row as the formula

If you select the cell & then click "Evaluate formula" on the formula tab, you can see what it's doing.

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#### bosco_yip

##### Well-known Member
It is a "Implicit Intersection" behavior in Excel, and try to Google for further detailing

Regards

#### joeu2004

##### Well-known Member
First, you should write =SUMPRODUCT(A1:A3,B1:B3) instead, which is normally-entered.

Second, =SUM(A1:A3*B1:B3) seems to work only if it is entered in row 1, 2 or 3. It is interpreted as =SUM(A1*B1), =SUM(A2*B2) or =SUM(A3*B3) respectively. And if that is the intent, there is no reason to uses the SUM function in that context. Simply write =A1:A3*B1:B3.

That interpretation is most useful for named ranges, e.g. "cost" defined as A1:A3 and "qty" defined as B1:B3, and your intent is to enter the formula =cost*qty for each of 3 transactions in rows 1, 2 and 3.

The point is: if you normally-enter =SUM(A1:A3*B1:B3) into any other row, you will get a #VALUE result, correctly informing you that the form is incorrect.

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#### tiredofit

##### Well-known Member
Thanks for all the explanation.

I don't normally write formulae like the second one, it was actually more out of curiosity than anything.

However, it is handy to find out exactly what it's doing, just in case I ever inherit someone else's spreadsheets.

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