TREE DIAGRAMS:
Example: If it rains on a given day, the probability that it rains the next day is 1/3. If it does not rain on a given
day, the probability that it rains the next day is 1/6. The probability that it will rain tomorrow is 1/5. What is the
probability that it will rain the day after tomorrow? Draw a tree diagram of all the possibilities to determine the
answer.
Answer:
Draw the first level of the tree diagram
Before we can determine what happens on the day after tomorrow, we first have to determine what
might happen tomorrow. We are told that there is a 1/5 probability that it will rain tomorrow. Here is
how to represent this information using a tree diagram:
Draw the second level of the tree diagram
We are also told that if it does rain on one day, there is a 1/3 probability that it will also rain on the
following day. On the other hand, if it does not rain on one day, there is only a 1/6 probability that it will
also rain on the following day. Using this information we complete the tree diagram: