I'm posting one puzzle, riddle, math, or statistical problem a day. Try to answer each one and post your answers in the comments section. I'll post the answer the next day. Even if you have the same answer as someone else, feel free to put up your answer, too!
Thursday, March 22, 2007
Five Balls Are Removed
A hat contains a number N of blue balls and red balls. If five balls are removed randomly from the hat, the probability is precisely 1/2 that all five balls are blue. What is the smallest value of N for which this is possible.