A tree diagram
is a diagram used to represent probabilities when two or more events
are combined.
Suppose for example, a bag contains 3 red balls and 2 black balls.
If two balls are drawn from the bag, one after the other,
then there are four possible outcomes, RR, RB, BR, BB. These
can be represented by a tree diagram, with the probabilities
of drawing each ball along the branches.
