How do you add a row of cells in two columns into a third column?

[Dari]

I know you can go to the first cell and do something like this in C1:
=SUM(A1:B1)

My problem is how do I extend this down without having to manually write this?

 

[ChAoTiCpInOy]

Bottom right of the cell, drag it to wherever it is how far you want to go down.

 

[Dari]

Originally posted by: ChAoTiCpInOy
Bottom right of the cell, drag it to wherever it is how far you want to go down.

Thanks. I figured that out shortly after posting this.

 

[NeoV]

even better - if you double-left click in the lower left corner of the cell with the formula, it will auto-copy it down to every row with corresponding data in row B

 

[Dari]

Originally posted by: NeoV
even better - if you double-left click in the lower left corner of the cell with the formula, it will auto-copy it down to every row with corresponding data in row B

Thank you as well.

 

[NeoV]

that should have said "lower right corner of the cell", not lower left