Discuss how to determine the formulas and functions needed for a worksheet.

What will be an ideal response?

As you have learned, formulas and functions simplify the creation and maintenance of worksheets because Excel performs calculations for you. When formulas and functions are used together properly, the amount of data that a user manually must enter in a worksheet greatly can be diminished:

• Utilize proper algebraic notation. Most Excel formulas are the result of algebraic calculations. A solid understanding of algebraic operators and the order of operations is important to writing sound formulas.
• Utilize the fill handle and copy and paste operations to copy formulas. The fill handle and the Excel copy and paste functionality help to minimize errors caused by retyping formulas. When possible, if a similar formula will be used repeatedly in a worksheet, avoid retyping the formula and instead use the fill handle.
• Be careful about using invalid and circular cell references. An invalid reference occurs when Excel does not understand a cell reference used in a formula, resulting in Excel displaying a #REF! error message in the cell.

A formula in a cell that contains a reference back to itself is called a circular reference. Excel often warns you when you create a circular reference. In almost all cases, circular references are the result of an incorrect formula. A circular reference can be direct or indirect. For example, placing the formula =A1 in cell A1 results in a direct circular reference. An indirect circular reference occurs when a formula in a cell refers to another cell or cells that include a formula that refers back to the original cell.

• Employ the Excel built-in functions whenever possible. Excel includes prewritten formulas called functions to help you compute a range of values and statistics. A function takes a value or values, performs an operation, and returns a result to the cell. The values that you use with a function are called arguments. All functions begin with an equal sign and include the arguments in parentheses after the function name. For example, in the function =AVERAGE(C4:C12), the function name is AVERAGE, and the argument is the range C4:C12. Become familiar with the extensive number of built-in functions. When you have the choice, always use built-in functions instead of writing and typing a formula version of your mathematical expression. Such a practice reduces the possibility of errors and simplifies the formula used in a cell, resulting in improved readability.