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.

(In reply to

Solution by hoodat)

**You say**:

""In order to be divisible by 50, two of the integers must be some combination of 5,10,15, & 20. There are 6 combinations of this [4!/(2!2!)]. Once one of these pairs is picked, there are 153 combinations of the remaining integers [18!/(2!16!)]. This yields 918 total"

**WRONG !!**

Where are (20,20,20,20) or (5,5,5,10) and hundreds of others you have missed???

PLEASE RECOUNT!

**P.S. Charlie's result is transparent and 100% correct.**

**Analytical verification is not so easy.**

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