Originally Posted by

**eysikal** So my professor gave **6 possible essay topics for the final exam**. Of these 6 he will choose 2 that will appear on the exam. **I am to choose 1 of the 2 essay topics he presents on the exam and respond to it.**

So I am strapped for time and wish to study as little as possible. So, naturally my first thought was to only study for 5/6 possible topics--ensuring that I would at least be able to answer one of the topics no matter what the professor chooses.

But what are the odds that if I only study for 4/6 possible topics that I will be left completely in the dark? (read: the 2 topics he choses are the 2 that I didn't prepare for.)

So, is this right?

For his first choice: 2/6 chance that he chooses one that I didn't prepare for.

For his second choice: 1/5 chance that he chooses one that I didn't prepare for.

Total probability = (2/6) * (1/5) = 6.67%

Also if, the above is right, then is it safe to assume that the odds that I know at least one of the 2 essay topics on the exam is = 100% - 6.67% = 93.33%?

Discuss.