Functions can be used as arguments to other functions. Combining functions in this way helps you to make the most of the data entered on your worksheet. It also takes advantage of the ability of Microsoft Excel to quickly calculate and recalculate formulas. Remember to type an equal sign at the beginning of every formula, but not before functions used as arguments to other functions.
For example, suppose you want to estimate your income tax bill for the next year based on your last three years' worth of tax records. The cells A1:A3 on your worksheet contain your taxable income for the last three years and the cells B1:B3 contain your tax rates for those years. Without re-entering any data that is already on your worksheet, you can estimate the tax you will owe next year by using the formula:
=PRODUCT(AVERAGE(A1:A3), AVERAGE(B1:B3))