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 1/4

  1. Add a zero to the number.
  2. Divide by 8.

   Example:

  1. If the 2-digit number chosen to multiply by 1 1/4 is 37:
  2. Add a zero: 370
  3. Divide by 8: 370/8 = 46 1/4
  4. So 37 x 1 1/4 = 46 1/4.

   See the pattern?

  1. If the number to be multiplied by 1 1/4 is 72:
  2. Add a zero: 720
  3. Divide by 8: 720/8 = 90
  4. So 72 x 1 1/4 = 90.
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