The following is provided by Mary.

Use a calculator and memorize the following steps, you can easily get the other's telephone number. Still, there are two shortfalls. First, you do not know what the area code is. Second, the phone number must be in the format of 999-9999 (seven digits).

Let's look at an example. FedEx's toll free number is 1-800-GoFedEx (or, 1-800-463-3339). Give a calculator to a FedEx agent and ask him punch in exactly as shown below. While he is keying, you don't even need to look at what he is doing. Just ask him follow your instructions correctly.

At this point, ask him to return the calculator to you. You divide the above number by 2. In this case, it is 9266678 / 2 = 4633339. Tell him his number is 463-3339 and leave him in a puzzle how you made it. J