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Counting Quadruplets III (Posted on 2011-02-06) Difficulty: 3 of 5
Determine the total number of quadruplets (A,B, C, D) of positive integers with A ≤ B ≤ C ≤ D ≤ 25, such that (A+B)*(C+D) is divisible by |A*D – B*C|, whenever A*D ≠ B*C.

Note: |x| refers to the absolute value of x.

No Solution Yet Submitted by K Sengupta    
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Some Thoughts re: computer solution ... Do me a favor , Charlie | Comment 2 of 6 |
(In reply to computer solution by Charlie)

Do me a favor ,  Charlie

I'®ve tried to evaluate manually  the total number of quadruplets (A,B, C, D) of positive integers with A <= B <= C <= D <= 25, and got 20175.

Tot= C(25,4)+25*C(24,2)+2*C(25,2)+25=20175

Please, check my result by adding another counter to your program and make me happy (or busy again).

Thank you.

Edited on February 7, 2011, 1:59 am
  Posted by Ady TZIDON on 2011-02-07 01:51:06

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