Pull 2 green marbles out of a bag containing three green and three blue marbles One pull.

Question

A bag contains six marbles: three blue and three green. What is the probability of blindly reaching into

the bag and pulling out two green marble on only one pull?

Answer 1

Even though they are pulled out simultaneously we can think of it sequentially

P(first marble is green) = 3/6

P(2nd marble is green) = 2/5 -- 2 green left and 5 total left after the first marble is chosen

so p = 3/6 * 2/5 = 1/5

If you are comfortable with the combination function (which you really want to be!). You can get the answer this way:

p = C(3,2) / C(6,2)