To calculate input/output tables, also known as function tables, first determine the rule. Use the rule to complete the table, and then write down the rule. You need a pencil and paper, and it takes about 10 minutes to complete the exercise.

**Create a rule for the table**Create a rule that tells you how one number relates to another. Represent the first number with "x" and the second with "y". An example of a rule is: x – 3 = y. Write down some numbers that fit with the rule. For example, you can write: 3 - 3 = 0 or 5 - 3 = 2.

**Complete the table**Create a table that is two cells high. Make enough cells for the width to hold all the numbers you want to use. In the first cell, write input. In the cell below it, write output. In the cell next to input, write the first value for "x". In the cell below that, write the first value for "y". Continue to fill out the table with sets of numbers that successfully complete your formula.

**Write down the rule**Write down the rule you created in the form of a complete sentence. For example, write, "If input is "x" and output is "y," then x - 3 equals y."