By dcb on Feb 28, 2005
Here is yet a different kind of puzzle. It will teach you (if you figure it out) how to solve another large class of logic puzzles. Enjoy. It isn't as easy as you might think!
Your Yellow Lab Retriever is having puppies!! You (Bill) watch as she quickly delivers two males. You run upstairs to grab your camera and the doorbell rings - two of your friends (Joe and Bob) have come over to visit. You mention that your dog has just given birth. After a little while you all go downstairs to see how the they are doing. On the way down, you mention to Joe (Bob doesn't hear) that there are two male puppies. When you return, a third has been born... a chocolate!! You now have one of each color. The yellow and black lab puppies (your friends don't know in which order they were born) tumble over each other and Joe notices that those two are boys. You challenge each other: What is the probability that all three puppies are male? Bob overhears the challenge, but he doesn't know the gender of any of the puppies.
Bill, Joe, and Bob all happen to be taking "Statistics 101" together at the local community collage. Over a beer they jot down their answers. They are all pretty bright students (assume they get it right) and competitive (they don't help each other or compare notes). What did they come up with?
If you give up, here is the solution: