**SUM**, and type an opening parenthesis in cell C9.

You can type cell references directly into cells, or you can enter cell references by clicking cells, which avoids typing errors.

In the first lesson you saw how to use the SUM function to add all the values in a column. You could also use the SUM function to add just a few values in a column, by selecting the cell references to include.

Imagine that you want to know the combined cost for video rentals and CDs in February. You don't need to store the total, so you could enter the formula in an empty cell and delete it later. The example uses cell C9.

The example shows you how to enter the formula. You would click the cells you want to include in the formula instead of typing the cell references. A color marquee surrounds each cell as it is selected and disappears when you press ENTER to display the result 45.94. The formula =SUM(C4,C6) appears in the formula bar near the top of the worksheet whenever cell C9 is selected.

The arguments C4 and C6 tell the SUM function what values to calculate with. The parentheses are required to separate the arguments from the function. The comma, which is also required, separates the arguments.