How to Add Formulas to iBooks Author Tables
You can let iBooks Author do the math for you within tables, just like you can in Excel or Numbers. But the ebook’s readers can’t adjust the calculations to experiment with values; instead, the calculations are a convenience for you, the author, to save some calculation effort.
There are three basic ways to apply formulas to cells in iBooks Author, and the first two begin in the Table inspector’s Format pane:

Select the cells to which you want to apply the formula, and then choose the desired calculation from the Formula popup menu: None, Sum, Min (minimum value in the set), Max (maximum value in the set), Average, Count (number of values in the set), and Product (which multiplies all the values in the set against each other).
If the cell selection goes across two or more rows, a new row is inserted below the selected cells, and each cell contains the results for the selected cells above. If the cell selection goes across two or more columns but just one row, a new column is inserted to the right of the selected cells, showing the formula’s results in the adjacent cell.

Select the cell where you want to place the results of a calculation, and then choose the desired calculation from the Formula popup menu or choose the Formula Editor option to enter your own calculation.
The Formula Editor lets you create more complex calculations, such as adding values across several rows and columns (to choose cells as inputs to your formula, you can dragselect the cells, as well as select individual cells with the pointer). You can also use a variety of other formulas, including trigonometric, accounting, and logical (if) formulas, including the same syntax that you would use in Excel or Numbers. Some portions of the formula have options you can apply; look for a small downpointing triangle to the right of the colored portions and click it to reveal its menu options.
After you enter the formula in the Formula Editor, click the green checkmark icon to the right of the formula to enter it or the red X icon (next to the green checkmark) to clear it.

Select a cell and choose Insert→Function, and then choose the desired formula, Formula Editor, or — available only here — Show Function Browser. The formulas and Formula Editor work just like they do in the preceding method. If you choose Show Function Browser, the Formula Editor appears over your selected cell, and the Function Browser, appears onscreen to give you a list of all the formulas available in iBooks Author, so you don’t have to rely on memory. Select a category from the list at left to see the available functions; click one to get a description of its use. Click the Insert Function button to add that selected function to the Formula Editor.