Adding numbers

I want to add b1 multiplied by b4 then add to that c1 multiplied by c4 and so on to give me a total is there a formular for this

=(B1*B4)+(c1*C4)

and so on

In B5 put this =Sum(B1*B4)
Then in C5 put this =B5+SUM(C1*C4)

Then copy C5 to D5 and E5 etc.

Is there a formular so if I have veriable number in column 1 and the same amount in column 4 I can multiply each row as ie b1 x b4 the add up all the individual totals to give me 1 answer with out putting in =sum(b1xb4,c1 xc4 ) as the equation would be quite long if z1xz4

Try
=SUMPRODUCT(B1:D1,B4:D4)