using sumproduct

[Guest]

I am trying to multiply elements of two arrays of length 10 and sum the 10
products. The first array is A1 - A10 (vertical). The second array is C1 -
L1 (horizontal). This formula works:
=A1*C1+A2*D1+A3*E1+A4*F1+A5*G1+A6*H1+A7*I1+A8*J1+A9*K1+A10*L1

I was told that this is dumb and to use sumproduct. So I try:
=SUMPRODUCT(A1:A10,C1:L1) and all it tells me is #VALUE!

Now I am sure that this is really simple, but I am stumped and will
appreciate and help anyone can give me.

 

[Guest]

The formula SUMPRODUCT needs the two arrays to be the same size, and in this
case they are not, even if they have the same number of elements (one is
10x1, other is 1x10). You can use the following array formula instead:
=SUM(A1:A10*TRANSPOSE(C1:L1))
Enter it with CTRL+SHIFT+ENTER

Hope this helps,
Miguel

 

[Guest]

It does help.
Thank you for your time & willingness to share it.