I have a file which has multiple rows. In each row, I need to do a calculation. For example, in cell D1, I write:

=(B1-A1)*C1

I then need to sum all the rows of that result, say:

=sum(D1:D30)

Is there a way to do this in a single cell instead of doing the calculation in each row of column D and then summing all the individual results?

I do not know enough about Excel to have tried this yet. I only know how to do it by doing the calculation in each row and then summing.