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Niners (Posted on 2002-10-23) Difficulty: 4 of 5
The set of numbers {9, 99, 999, 9999, ...} has some interesting properties. One of these has to do with factorization. Take any number n that isn't divisible by 2 or by 5. You will be able to find at least one number in the set that is divisible by n. Furthermore, you won't need to look beyond the first n numbers in the set.

Prove it.

(from http://www.ocf.berkeley.edu/~wwu/riddles/)

See The Solution Submitted by levik    
Rating: 4.2500 (8 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Some Thoughts Hmmm... | Comment 3 of 15 |
all numbers divisible by 2 and 5 dont have a '9' at the end. All the others may have. So I guess those numbeer's multiples will eventually be one of the set's.
  Posted by Dulanjana on 2002-10-23 14:54:29
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