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 4 1/2

  1. Select a 2-digit number.
  2. Multiply the number by 2.
  3. Divide the product by 9.

   Example:

  1. The 2-digit number chosen to divide by 4 1/2 is 62.
  2. Multiply by 2: 2 x 62 = 124
  3. Divide by 9: 124/9 = 13 7/9
  4. So 62 divided by 4 1/2 = 13 7/9.

   See the pattern?

  1. The 2-digit number chosen to divide by 4 1/2 is 36.
  2. Multiply by 2: 2 x 36 = 72
  3. Divide by 9: 72/9 = 8
  4. So 36 divided by 4 1/2 = 8.

For numbers not divisible by 9, your calculator will get a repeating decimal, but your fractional answer will be exact.


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7 January 2000
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