Question

ANYONE SMART AT MATH NEED HELP ON THIS

A bag of marbles contains 6 blue marbles and 1 green marble. Mary and Frank will draw a blue marble followed by a green marble, without replacing the first marble. Mary says the probability will be 6/49, and Frank says that the probability will be 1/7. Who is correct? Explain and justify your answer by showing work.
---------------Is correct because___

Answer 1

Frank is correct, because (see explanation below)

Explanation:

Let's separate into two cases:

Case 1: Blue marble

`(6)/(7)` (There are 6 blues in the bag and 7 marbles in total in the bag, we put the 6 in the numerator because we want a blue marble first.)

Case 2: Green marble

`(1)/(6)` (There is only 1 green in the bag and 6 marbles remaining in the bag, because we already took 1 blue out in Case 1. We put 1 in the numerator because we want the green marbloe only.)

Multiply Case 1 with Case 2 because they are a combination:

`(6)/(7) * (1)/(6) = (1)/(7)`

Therefore Frank is correct.