Unexam #1

Given in class on November 10, 2005.

Q: How many 7 card hands have exactly two 3-of-a-kinds?

A: 54,912

Obviously the point of this exercise is not to test your counting skills, it is to force you to explain yourself when you use some of the things we've learned in class.  Given that we have so many examples just like this in class and on the FORUM I expect that this first exercise should be easy, short and sweet.  Here are some remarks about what I am looking for in your explanations.  I expect that the other unexams will be a bit more difficult to explain.  I will give you one more unexam to do over the December break.

1) Your answer should be clear, complete and correct.

I am looking for an explanation which is inarguably correct.  You should include all details necessary to explain why the answer matches the question.  Every sentence should either be an obviously true statement or follow from what you wrote before.  Ask yourself the question 'why?' at the end of each statement and the text that you have written should answer that question.

2) Your answer should be short.

This should take no more than 3-4 clear sentences.  If it takes you 2 pages to explain the answer 54,912 then your answer is probably not very clear.

3) If you have any questions please ask me.  Please don't ask me to tell you if your answer is correct or not so that you can redo it.

I also want you to be able to recognize when you have answered the question.  It isn't fair that you have multiple tries.