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Dividing the Unknown (Posted on 2004-05-20) Difficulty: 2 of 5
Consider the long division shown... (The digits in the blanks can be any digit and ? represents a number that can have any amount of digits.)

Although the number of digits in the divisor is not given, there is only 1 solution to this fairly easy division. Find the dividend, the divisor, and the quotient.

See The Solution Submitted by Victor Zapana    
Rating: 3.2500 (4 votes)
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Solution Full Solution Comment 2 of 2 |
1091889708 ÷ 12 = 90990809

Since 8 times the divisor produced a two-digit number, the divisor must be at least 2 and at most 12. Also, since it produced a three-digit result in other places, it must be a 12, and the digit in the dividend in those spots must be a 9:

        9 _ 9 9 _ 8 _ 9
12  _ _ _ _ _ _ _ _ _ _
    1 0 8
        _ _ _
        1 0 8
          _ _ _
          1 0 8
              0 _ _
                9 6
                  _ _ _
                  1 0 8
                      0
In the two spots where subtracting 108 left a zero, the number above must obviously be 108 as well:
        9 _ 9 9 _ 8 _ 9
12  _ _ _ _ _ 8 _ _ 0 8
    1 0 8
        _ _ _
        1 0 8
          1 0 8
          1 0 8
              0 _ _
                9 6
                  1 0 8
                  1 0 8
                      0

Similarly, the other blanks must obviously be filled in with 118 (- 108 = 10) and 97 (- 96 = 1) :

        9 0 9 9 0 8 0 9
12  _ _ _ 1 8 8 9 7 0 8
    1 0 8
        1 1 8
        1 0 8
          1 0 8
          1 0 8
              0 9 7
                9 6
                  1 0 8
                  1 0 8
                      0

Finally, the first three digits of the number must be 109 (to leave a one when 108 is subtracted) :

        9 0 9 9 0 8 0 9
12  1 0 9 1 8 8 9 7 0 8
    1 0 8
        1 1 8
        1 0 8
          1 0 8
          1 0 8
              0 9 7
                9 6
                  1 0 8
                  1 0 8
                      0

  Posted by DJ on 2004-07-21 00:07:43
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