A box contains four stones: one white, one yellow, and two blue.
I put my hand into the box and pick up two stones.
I bring my hand out in a fist, look inside my fist and remove a blue stone.
What is the probability that the other stone in my hand is also blue?
The problem is small enough to LIST all the outcomes.
The four stones are:.
There are six possible outcomes:
We are told that one of the two stones is blue.
The sample space is reduced to five outcomes:
The stones are both blue in exactly one case.