Possible to SUM() results of a formula in each cell?

[JohnKauffman]

This is easy to do by adding a col, can I do it all in a formula?

I have a sheet where rows = meetings. Each meeting has several sessions. Column A is “number of sessions” and a column B “Length of one session (hrs.)”. I would like to get a sum of all the hours for all the sessions for all the meetings. I know I could add a column C of A*B and sum that. But I’m curious if I can do it in one formula using only cols A and B.

Is there a way to sum the results of a formula in each cell of the range to be summed? Maybe along the lines of =SUMFORMULA(A1:B100,=A*B)?

Is this the question that will lead me to start studying arrays?

 

[Jonmo1]

Perhaps
=SUMPRODUCT(A1:A100*B1:B100)

or just
=SUMPRODUCT(A1:A100,B1:B100)