When Intuition is Wrong and Math is Right
Got two math puzzles, see if you can figure it out 
FTA:
Alice secretly picks two different real numbers by an unknown process and puts them in two (abstract) envelopes. Bob chooses one of the two envelopes randomly (with a fair coin toss), and shows you the number in that envelope. You must now guess whether the number in the other, closed envelope is larger or smaller than the one you’ve seen.
Is there a strategy which gives you a better than 50% chance of guessing correctly, no matter what procedure Alice used to pick her numbers?
Second one. FTA:
I have two children, one of whom is a son born on a Tuesday. What is the probability that I have two boys?
Answers are in the links. Damn these puzzles. Anybody got a good source of puzzle like these?