multiplying and adding

[demolay]

i have two collumns: A and B
there are some numbers in these collumns and many rows...
i want to do the following in a different single row:
(A1*B1)+(A2*B2)+(A3*B3)+...
is there any shortcut of it? any formula? any suggestions?..

example:
Column A----Column B
1--------------21
5--------------63
3--------------31
7--------------65
.....
i want a value in Column C1 which will give me
=(1*21)+(5*63)+(3*31)+(7*65)...
i guess you got it

 

[Jerry W. Lewis]

=SUMPRODUCT(A1:A4,B1:B4)

Jerry

 

[Dan C.]

A handy note.

To get the Weighted Average of the one of the columns,
divide it by the total of one column.

=SUMPRODUCT(A1:A4,B1:B4)/B5

Column A B
UPB Interest
100 5.000
200 5.500
300 6.000
Total 600 =SUMPRODUCT(A1:A4,B1:B4)/B5 = 5.6667

 

[Harlan Grove]

To get the Weighted Average of the one of the columns,
divide it by the total of one column.

=SUMPRODUCT(A1:A4,B1:B4)/B5

Column A B
UPB Interest
100 5.000
200 5.500
300 6.000
Total 600 =SUMPRODUCT(A1:A4,B1:B4)/B5 = 5.6667

....

Shouldn't the formula be

=SUMPRODUCT(A1:A4,B1:B4)/A5

??