# Probability

• Oct 29th 2006, 07:11 AM
413
Probability
At a certain university, 30% of the students major in math. Of the students majoring in math, 60% are males. Of all the students at the university, 70% are males.
a) What is the probability that a student selected at random in the university is male and majors in math?

b) What is the probability that a randomly selected student in the university is female or majors in math or both?

I got a) as 18%, I am not sure how to do b).
• Oct 29th 2006, 07:15 AM
ThePerfectHacker
Quote:

Originally Posted by 413
At a certain university, 30% of the students major in math. Of the students majoring in math, 60% are males. Of all the students at the university, 70% are males.
a) What is the probability that a student selected at random in the university is male and majors in math?

b) What is the probability that a randomly selected student in the university is female or majors in math or both?

I got a) as 18%, I am not sure how to do b).

Make it simple.
Let, the number of students to 100.
Then, 30 are for math.
18 are male math.
70 males altogether.
So, 52 are males not in math.
• Oct 29th 2006, 11:05 AM
413
so 30% are females, 30% majors in male and 12% are female and majors in math...

therefore:
=P(female)+P(math major)+P(female and math major)
=30% +30 %+12%

=72% correct?
• Oct 29th 2006, 11:13 AM
CaptainBlack
Quote:

Originally Posted by 413
so 30% are females, 30% majors in male and 12% are female and majors in math...

therefore:
=P(female)+P(math major)+P(female and math major)
=30% +30 %+12%

=72% correct?

b) What is the probability that a randomly selected student in the university is female or majors in math or both?

There are 30 female students and 18 math majors who are not female (as
the female math majors have already been counted we don't count them
again), so there are 48 students who satisfy the criteria out of 100, so the
0probability is 48%.

RonL