Help please on another excel question...

[Justin7]

I have two columns - A and B. I want to get the sum of the products of these rows
i.e. A1*b1 + a2*b2 + a3*c3 ... a9*b9

I'll be repeating this formula in different places, so I don't want to manually do that. Is there an easy command to do that? I can't seem to get sum working properly with it.

[Pancho sanza]

why does it jump from a*b to a*c (3rd formula)?

[LT Profits]

Why not just put the products of A and B in C? Then the simple formula would be sum(c1.c9)

[LT Profits]

why does it jump from a*b to a*c (3rd formula)?

I think it was just a typo and he meant a3*b3

[Justin7]

Yes, meant to be a3*b3.

I'd prefer to do it without an extra column - I am using this calculation a lot.

[Pancho sanza]

CELL C1

=SUM(A1*B1)

CELL C2

=SUM(A2*B2)+C1

CELL C3

=SUM(A3*B3)+C2


Once you fil in cell C2, just copy down

[LT Profits]

He said he didn't want third column.

[Justin7]

CELL C1

=SUM(A1*B1)

CELL C2

=SUM(A2*B2)+C1

CELL C3

=SUM(A3*B3)+C2


Once you fil in cell C2, just copy down

That works, but it adds another column.

Anyway to do this in one cell?

[Pancho sanza]

He said he didn't want third column.

Where will he show the output?

[Data]

=SUMPRODUCT(A1:An*B1:Bn)

[Justin7]

=SUMPRODUCT(A1:An*B1:Bn)

Data, you're an excel machine! Thanks, this is exactly what I was looking for.

[LT Profits]

=SUMPRODUCT(A1:An*B1:Bn)

Thanks!

I didn't even know a SUMPRODUCT function existed.

[Pancho sanza]

Oh, thats what you meant.

That was my next answer.

So Data is the excel guru around here, good to know.

[Data]

Justin7, LT Profits, no problem.

Pancho sanza, I am not a guru, just got some experience with it while working on my data, so, I try to help when I can.