Probability question

Question

all of the students in a history class are juniors or seniors. there are twice as many girls as in the class, and there are 3 times as many senior girls as junior girls. If a student is selected at random, what is the probability that the student is a junior girl?

Answer 1

Do you mean "...there are twice as many girls as BOYS"?

 

If so, then...

 

2/3 of the students are girls, and 1/3 are boys.

 

3/4 of the girls are seniors and 1/4 are juniors.

 

So 1/4 of 2/3 is the fraction of the class that is junior girls.  1/4 * 2/3 = 1/6.  So the probability that a randomly selected student is a junior girl is 1/6.