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Counting Quadruplets (Posted on 2010-08-20) Difficulty: 3 of 5
Each of A, B, C and D is a positive integer with the proviso that A ≤ B ≤ C ≤ D ≤ 20.

Determine the total number of quadruplets (A, B, C, D) such that A*B*C*D is divisible by 50.

No Solution Yet Submitted by K Sengupta    
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Some Thoughts re: Solution -- ERR0NEOUS | Comment 8 of 11 |
(In reply to Solution by Praneeth)

TOTALLY WRONG:

Case 1: 4 chosen from p 

 NOT NECESSERALLY DISTINCT,BUT

MUST INCLUDE 5^2 AND 2  
So: 
  20,20,20,20  15,15,15,20  10,15,15,20  10,10,15,20 
10,10,10 ,10,    5,10,10,10   ETC  ARE OK

5,5,5.15  5,5,5.5 ARE not OK 

 
Count them ,it is more than 1

So are other cases

 

 



 

 


  Posted by Ady TZIDON on 2010-08-20 20:09:33
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