An urn contains 5 black and 20 white marbles. They are to be drawn one at a time until all of one color has been exhausted.
What is the probability that the color of the first draw correctly predicts the first color exhausted?
(In reply to re. difficulty level
by Ady TZIDON)
Difficulty level is rather a subjective matter. I've noted in the past that the D-levels you usually assign are lower than what I'd consider appropriate, most recently "Clever Counting". When voting I take this into consideration, and would never insist on a change of D level, first of all, as in the case of a D level I consider too low, there might be an insight I might not see.
In the case of the current puzzle, I knew there'd be a little consideration of the two cases, so maybe it could go to a D2, but nothing higher, especially considering some of the difficult (to me) puzzles you have insisted are no higher than D2. At D1, therefore, the current puzzle is only one D-level off (for me).
It may be that I just have more of an affinity for probability puzzles. Your area might be different. That's whay haggling over difficulty levels isn't worth the time involved, unless, say we suspect (which is most often the case the case of a "wrong" difficulty level) that the author has merely left the default difficulty of 3, and it's clearly much higher or lower. Even then, a comment is sufficient rather than withholding a vote.
Posted by Charlie
on 2015-08-12 08:57:18