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 2-digit number by 2 1/3

  1. Select a 2-digit number.
  2. Multiply the number by 7.
  3. Divide by 3.

   Example:

  1. The 2-digit number chosen to multiply by 2 1/3 is 67.
  2. Multiply by 7: 7 x 67 = 420 + 49 = 469.
  3. Divide by 3: 469/3 = 156 1/3.
  4. So 67 x 2 1/3 = 156 1/3.

   See the pattern?

  1. The 2-digit number chosen to multiply by 2 1/3 is 91.
  2. Multiply by 7: 7 x 91 = 630 + 7 = 637.
  3. Divide by 3: 637/3 = 212 1/3.
  4. So 91 x 2 1/3 = 212 1/3.


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22 February 1999
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