In a mathematics course that I teach, there is an advanced unit in counting combinatorics. As a cooperative assessment, I give the kids the odds against being dealt all possible five-card hands in a game of poker. Their job is to prove those odds, complete with a detailed explanation. I do this in groups of three and the discussions that lead them to their solutions are very interesting. This activity usually takes the students three fifty-minute class periods, but the students really enjoy the challenge. It has been a rewarding experience.