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 3 3/4

  1. Select a 2-digit number.
  2. Multiply the number by 30.
  3. Divide by 8.

   Example:

  1. The 2-digit number chosen to multiply by 3 3/4 is 24.
  2. Multiply by 30: 24x30 = 600+120 = 720.
  3. Divide by 8: 720/8 = 90.
  4. So 24 x 3 3/4 = 90.

   See the pattern?

  1. The 2-digit number chosen to multiply by 3 3/4 is 52.
  2. Multiply by 30: 52x30 = 1500+60 = 1560.
  3. Divide by 8: 1560/8 = 195.
  4. So 52 x 3 3/4 = 195.


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15 November 1999
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