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Old 12-17-2004, 04:20 PM  
garfield81
Confirmed User
 
Join Date: Feb 2004
Location: Sin City, NV
Posts: 212
Quote:
Originally posted by alexg
Well, not really a riddle, but a rather interesting and not so easy to understand fact....


Let's say there's a show on TV where the participant has to chose 1 out of 3 closed boxes. In one of them there are $10k, and the other 2 are empty.

He makes a choice, and before opening the box the host of the show opens one of the two other boxes which is empty (there must be at least one, because a total of 2 boxes out of the 3 are empty).

now, should the participant change his choice to the other last box that the host didn't open? or should he stay with his choice?

most would think it doesn't matter at all... but the correct answer is that he should switch...

why?

at the beginning the participant was to chose one of 3 boxes... one of the three contained the cash, therefore he had a 33.333...% of chosing the right one...
now, after the participant has opened one of the empty boxes, if he changes his choice... then he has to chose 1 out of 2 boxes, and has a 50% chance to get it right...
but if he stays with his old choice, he still has a 33.333% chance of course...

it doesn't remain 33.333% it changes to 50% because there are only 2 boxes. no need to get all complicated on it it's just trivial.
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