Apple Numbers '09 - Manual (Page 120)

The results of calculations using the values in those cells are instantly displayed in the
lower left corner of the window.
The results in the lower left are
based on values in these two
selected cells.
sum: Shows the sum of numeric values in selected cells.
avg: Shows the average of numeric values in selected cells.
min: Shows the smallest numeric value in selected cells.
max: Shows the largest numeric value in selected cells.
count: Shows the number of numeric values and date/time values in selected cells.
Empty cells and cells that contain types of values not listed above aren’t used in
the calculations.
2 To perform another set of instant calculations, select different cells.
If you find a particular calculation very useful and you want to incorporate it into a
table, you can add it as a formula to an empty table cell. Simply drag sum, avg, or one
of the other items in the lower left to an empty cell. The cell doesn’t have to be in the
same table as the cells used in the calculations.
Using Predefined Quick Formulas
An easy way to perform a basic calculation using values in a range of adjacent table
cells is to select the cells and then add a quick formula using the pop-up menu visible
when you click Function in the toolbar.
Sum: Calculates the sum of numeric values in selected cells.
Average: Calculates the average of numeric values in selected cells.
Minimum: Determines the smallest numeric value in selected cells.
120 Chapter 6 Using Formulas in Tables