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Marbles Bonanza (Posted on 2003-09-08) Difficulty: 4 of 5
You have an empty container, and an infinite number of marbles, each numbered with an integer from 1 to infinity.

At the start of the minute, you put marbles 1 - 10 into the container, then remove one of the marbles and throw it away. You do this again after 30 seconds, then again in 15 seconds, and again in 7.5 seconds. You continuosly repeat this process, each time after half as long an interval as the time before, until the minute is over.

Since this means that you repeated the process an infinite number of times, you have "processed" all your marbles.

How many marbles are in the container at the end of the minute if for every repetition (numbered N)

A. You remove the marble numbered (10 * N)

B. You remove the marble numbered (N)

See The Solution Submitted by levik    
Rating: 3.6154 (13 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: Respectfully, I disagree with someone. Maybe. | Comment 23 of 87 |
(In reply to Respectfully, I disagree with someone. Maybe. by Sam)

Sam, you wrote, "saying that premises are logically incoherent is not running away from the question, but can be an equally valid answer."

Agreed.

But while this problem doesn't describe something that is physically possible, it is not logically incoherent. (Unless you consider calculus and limits of Riemann sums also logically incoherent.)

So... stating that this problem's premises are logically incoherent is not "running away from the question", but it *is* wrong.
__________

As for what happens "if you could stop, you would have a finite set"... , well heck yeah. If you stopped after any particular iteration, we could specify exactly which marbles are in, and which are not in the container. But that is a completely different problem.

--- SK
  Posted by SilverKnight on 2003-09-09 21:04:42

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