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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   Dividing a 2-digit number by 1 3/7

  1. Select a 2-digit number.
  2. Multiply it by 7.
  3. Move the decimal point 1 place to the left.

   Example:

  1. The number chosen to multiply by 1 3/7 is 36.
  2. Multiply by 7: 7 x 36 = 210 + 42 = 252
  3. Move the decimal point 1 place to the left: 25.2
  4. So 36 divided by 1 3/7 = 25.2.

   See the pattern?

  1. The number chosen to multiply by 1 3/7 is 51.
  2. Multiply by 7: 7 x 51 = 357
  3. Move the decimal point 1 place to the left: 35.7
  4. So 36 divided by 1 3/7 = 35.7.


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