To add up the total of expenses for January, you don't have to type all those values again. Instead, you can use a prewritten formula, called a function.
You can get the January total in cell B7 by clicking Sum 
in the Editing group on the Home tab. This enters the SUM function, which adds up all the values in a range of cells. To save time, use this function whenever you have more than a few values to add up, so that you don't have to type the formula.
Pressing ENTER displays the SUM function result 95.94 in cell B7. The formula =SUM(B3:B6) appears in the formula bar whenever you click in cell B7.
B3:B6 is the information, called the argument, that tells the SUM function what to add. By using a cell reference (B3:B6) instead of the values in those cells, Excel can automatically update results if values change later on. The colon (:) in B3:B6 indicates a cell range in column B, rows 3 through 6. The parentheses are required to separate the argument from the function.
The next two lessons explain cell references and functions in more detail.
Tip The Sum button is also on the Formulas tab. You can work with formulas no matter what tab you work on. You might switch to the Formulas tab to work with more complex formulas, which are explained in other training courses.
