Phone Number Calculations

Here's one of those mathematical oddities that somewhat masquerades as a magic trick. Your spectator, with calculator in hand, performs a series of calculations. And surprise, at the end, he or she is looking at their telephone number. We walk you through the steps and at the end, display them all on a single page that you may print out.

Secret: Some mathematical oddity. Ask a math whiz, not a magician.

Ask your spectators to grab their calculators and enter the first three digits of their telephone numbers. Be sure that they enter the first three digits of their actual phone number, not the area code. As an example, we'll use the fictional phone number of 555-1212.

Enter 555
Ask them to multiply by 80.

555 x 80 = 44400

Ask them to add 1.

44400 + 1 = 44401
Ask them to multiply by 250.

44401 x 250 = 11100250

Ask them to add the last four digits of their telephone number. And then add the same number again.

11100250 + 1212 = 11101462

11101462 + 1212 = 11102674

Ask them to subtract 250

11102674 - 250 = 11102424

Ask them to divide by 2. If they've done everything correctly, they'll be looking at their telephone number.

45113 / 2 = 5551212

Here are the steps again:

Enter the first three digits of their phone number
Multiply by 80
Add 1
Multiply by 250
Add the last four digits of their telephone number.
Add the last four digits of their telephone number again.
Subtract 250
Divide by 2