BEATCALC:  Beat the Calculator!

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Back to Calculation Tips & Tricks
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From the BEATCALC mailing list:
a weekly service from B. Lee Clay, archived here by the Math Forum.
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   Multiplying a repeating 9-digit number by 3,
                   then dividing by 12345679

  1. Choose a repeating 9-digit number (one whose numbers are all the same).
  2. Multiply one digit by 9.
  3. Multiply by 3.

   Example:

  1. If the first number is 333333333:
  2. Multiply one digit by 9: 3 x 9 = 27.
  3. Multiply 3: 27 x 3 = 81.
  4. So 333333333 x 3 / 12345679 = 81.

   See the pattern?

  1. If the first number is 666666666:
  2. Multiply one digit by 9: 9 x 6 = 54.
  3. Multiply 3: 54 x 3 = 162.
  4. So 666666666 x 3 / 12345679 = 162.

Change the second multiplier to other numbers and create many variations of this exercise.


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21 April 1997
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