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Counting triplets (Posted on 2010-03-31) Difficulty: 3 of 5
For how many ordered triplets (a, b, c) of positive integers, each less than 10 is the product abc divisible by 20?

See The Solution Submitted by Ady TZIDON    
Rating: 4.0000 (1 votes)

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Solution (interpretations) | Comment 1 of 7

I assume "ordered" means "not decreasing" -- then there are 20 triplets.  Six of these have a repeated integer, so if those are excluded, the answer would be 14.

 


  Posted by ed bottemiller on 2010-03-31 12:23:44
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