Brain Teasers wanted

[AbelM]

For a riddle in the magazine of my student association (physics, mathematics and computer science students) i'm looking for some probability riddles. A good example would be this one which was posted some time ago in this forum.

Another good example would be the famous "three door problem"

Does anyone know some similar riddles? It's quite important that they aren't well known and not easily found on google.

Thanks in advance!

[LetYouDown]

Dunno if this will help, as it's obviously publicly available. http://perplexus.info/category/4/

I love that site, use it every day on my break to kill time. Some extremely difficult problems on there. You can always reword things so that they're not easy to google.

HTH

[Siegmund]

My personal favorite:

Choose a point X at random from the Cantor Set. (More formally, let X be a random variable whose distribution function is the Devil's Staircase.)

Find the mean (easy) and the variance (not too hard, but you have to find the right trick) of X.

[gaming_mouse]

[ QUOTE ]
My personal favorite:

Choose a point X at random from the Cantor Set. (More formally, let X be a random variable whose distribution function is the Devil's Staircase.)

Find the mean (easy) and the variance (not too hard, but you have to find the right trick) of X.

[/ QUOTE ]

I like that one. Will you post, or PM me, the solution.