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 625

  1. Select a 2-digit number.
  2. Multiply by 8.
  3. Divide the product by 5.
  4. Move the decimal point 3 places to the left.

   Example:

  1. The 2-digit number chosen to divide by 625 is 65.
  2. Multiply by 8: 8 x 65 = 480 + 40 = 520
  3. Divide by 5: 520/5 = 104
  4. Move the decimal point 3 places to the left: .104
  5. So 65 divided by 625 = .104.

   See the pattern?

  1. The 2-digit number chosen to divide by 625 is 32.
  2. Multiply by 8: 8 x 32 = 240 + 16 = 256
  3. Divide by 5: 256/5 = 51.2
  4. Move the decimal point 3 places to the left: .0512
  5. So 32 divided by 625 = .0512.


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8 May 2000
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