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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   Squaring special numbers (7 and
                 repeating 3's)

  1. Choose a number with a 7 and repeating 3's.
  2. The square is made up of:
    • first digits: 53 & one fewer 7 than repeating 3's
    • next digits: 2 & one fewer 8 than repeating 3's
    • last digit: 9

   Example:

  1. If the number to be squared is 7333:
  2. The square has:

    first digits: 53 and one fewer
        7 than 3's                 5 3 7 7
    next digits: 2 and one fewer
        8 than 3's                        2 8 8
    last digit: 9                                 9

  3. So 7333 x 7333 = 53,772,889.

   See the pattern?

  1. If the number to be squared is 733333:
  2. The square has:

    first digits: 53 and one fewer
       7 than 3's             5 3 7 7 7 7
    next digits: 2 and one fewer
       8 than 3's                        2 8 8 8 8
    last digit: 9                                    9

  3. So 733333 x 733333 = 537,777,288,889.
     


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12 July 1999
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