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 1 1/5

  1. Select a 2-digit number.
  2. Multiply the number by 6.
  3. Divide the product by 5.

   Example:

  1. The 2-digit number chosen to multiply by 1 1/5 is 34.
  2. Multiply by 6: 6 x 34 = 180 + 24 = 204
  3. Divide the product by 5: 204/5 = 40.8
  4. So 34 x 1 1/5 = 40.8.

   See the pattern?

  1. The 2-digit number chosen to multiply by 1 1/5 is 61.
  2. Multiply by 6: 6 x 61 = 366
  3. Divide the product by 5: 366/5 = 73.2
  4. So 34 x 1 1/5 = 73.2.


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11 September 2000
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