I completely confused on this my problem is this:

Richard has just been given a 10 question multiple-choice quiz in his history class. Each question has 5 answers, of which only one is correct. Since Richard has not attended class recently, he doesn't know any of the answers. Assuming that Richard guesses on all 10 questions, find the indicated probabilities.
a.) What is the probability that he will answer all questions correctly?
b.) What is the probability tha the will answer all questions incorrectly?
c.) What is the probability tha the will answer at least one of the questions correctly? Compute this two ways, first using the rule for mutually exclusive events and then use the fact that P(r> 1) = 1 - P(r=0).
d.) What is the probability that Richard will answer at keast half the questions correctly?

I have no idea what I am supposed to do with this problem my professor suggested this site to me for help. I really hope that someone can help me understand what I should be doing.
Thanks, Cheri

Cheri,

You're in luck.

Go to the Examples section on this site, and look at my post on Binomial Probabilities. There is an example problem I explain that is almost exactly like this one.

Try following my example in order to answer your question.

If you're still stuck, let us know and we'll provide a bit more guidance.

JohnM

Thank you that example does help a lot. Thanks again, Cheri