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Concatenated Numbers and Divisibility (Posted on 2010-06-29) Difficulty: 2 of 5
Each of p and q is a 6-digit base ten positive integer with no leading zero. The 12-digit number that is obtained by writing p and q side-by-side is divisible by the product p*q.

Determine all possible pair(s) (p, q) for which this is possible.

See The Solution Submitted by K Sengupta    
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More analytics | Comment 3 of 7 |
1) n = (1000000p + q)/pq , where n is a integer
    
2) Multiplying by q,     
   qn = 1000000 + (q/p)
   
   Since qn is an integer, so is q/p.

   (Yes, Ed, q must be a multiple of p)
   
   Let q/p = k, where k must be an integer between 1 and 9.
   
3) Since q is between 100000 and 999999
   And qn is between 1000001 and 1000009
   
   It follows that n must be between 2 and 10
   
4) q = (1000000 + k)/n
    p = (1000000 + k)*(k/n), so k must be less than n

This led to a relatively short search.  Unless I made a mistake in Excel, there are no solutions.

  Posted by Steve Herman on 2010-06-29 15:02:54
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