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To do a cool calculator trick, start by writing the number 73 on a piece of paper and folding the paper in half. Hand the paper to a volunteer, but don't let them look at what's on it! Then, ask your volunteer to enter a 4-digit number into a calculator twice so there's an 8-digit number on the screen. When they're finished, ask them to divide the 8-digit number by 137 on the calculator. Now, ask them to divide that number by the original 4-digit number they entered. If they followed your instructions, the final number on the calculator should be 73, regardless of the number they entered at the beginning. Tell them to look at the number on the sheet of paper they're holding. They'll be amazed that you predicted the right number! To learn how to read someone's mind using a calculator, keep reading!