How To Do the Calculator Prediction Trick

  • February 26, 2010
  • 1,783 Views
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Your friends will think you can read minds when you use only a calculator to guess their secret number.

You Will Need

  • A friend
  • Paper
  • A pen
  • A calculator
How To Do the Calculator Prediction Trick: Have friend write a number

Step 1: Have friend write a number

Tell your friend to write any number on a sheet of paper. The number can be as many digits long as they want.

Have each person in a group contribute one digit to form a final number that you can use in the trick.

How To Do the Calculator Prediction Trick: Write the number nine

Step 2: Write the number nine

Tell your friend you will predict the final number they will have at the end of the trick. Write the number nine on another sheet of paper, fold the paper, and set it aside.

How To Do the Calculator Prediction Trick: Scramble the digits

Step 3: Scramble the digits

Have your friend scramble the digits of their number and write it down. If the original number is 435, they might write down 354.

Have your friend write the larger of the two numbers above the other number to avoid getting a negative total when you subtract.

How To Do the Calculator Prediction Trick: Subtract

Step 4: Subtract

Have your friend use the calculator to subtract one number from the other.

How To Do the Calculator Prediction Trick: Add

Step 5: Add

Have your friend add the digits of the number together until only one digit is left.

Be sure that your friend uses the calculator when doing the math calculations. This trick won’t work if the math is wrong.

How To Do the Calculator Prediction Trick: Show your prediction

Step 6: Show your prediction

Show your friend your prediction on the piece of paper. Ask, “Is this your final number?” and prepare to watch their jaws drop in amazement at your magic skills.

A Greek mathematician in the second century invented the basis of modern algebra when he began using symbols for representation in math problems.

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