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 (4 and
                 repeating 6's)

  1. Choose a number with a 4 and repeating 6's.
  2. The square is made up of:
    • first digits: 21 & one fewer 7 than repeating 6's
    • next digits: 1 & one fewer 5 than repeating 6's
    • last digit: 6

   Example:

  1. If the number to be squared is 4666:
  2. The square has:

    first digits: 21 and one fewer
        7 than 6's                   2 1 7 7
    next digits: 1 and one fewer
        5 than 6's                          1 5 5
    last digit: 6                                 6

  3. So 4666 x 4666 = 21,771,556.

   See the pattern?

  1. If the number to be squared is 466666:
  2. The square has:

    first digits: 21 and one fewer
       7 than 6's             2 1 7 7 7 7
    next digits: 1 and one fewer
       5 than 6's                        1 5 5 5 5
    last digit: 6                                  6

  3. So 466666 x 466666 = 217,777,155,556.
     


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21 December 1998
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