Question 1071751
A lock has a disk with 31 numbers written around its edge. The combination to the lock is made up of three numbers (such as 12-33-07 or 19-19-08). How many different possible combinations are there for this lock? 
What is the probability of randomly guessing the correct one? 
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If there is no repetition of numbers the answer is 31P3 = 31*30*29
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Cheers,
Stan H.
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