# Easy probability ..

I want to make sure these answers are correct

A class has 10 freshmen, 8 sophomores, and 12 seniors. On a recent test, 3 freshmen, 5 sophomores and 3 seniors got an A.

a) What is the probability that a paper picked at random is an A paper?

11/30

b) What is the probability that a paper picked at random is by a sophomore but not an A?

3/30

c) What is the probability that an A paper is by a senior?

3/12

• I think you meant 3/11 for c ? – user99680 Dec 5 '13 at 23:57

The answers are correct, except for c), it would rather be $3/11$ as there are $11$ members with $A$ class.