After completion of this chapter, students will be able to:

  • find the probability of mutually exclusive event by additive and multiplication law.
  • illustrate the probability on tree diagram.



A die is a well-balanced cube with its six faces marked with numbers (dots) from 1 to 6. It has a chance of happening events consisting of the single element is \(\frac{1}{6}\).An unbiased coin has 50% chance of happening the event 'H' and 'T'. i.e. \(P(H) = \frac{1}{2} = P(T)\).

Tree Diagram

the probability of tree diagram can be done by using two methods. 1st and 2nd. When we deal the problems of probability that involves two or more stages, it is frequently useful to use probability tree diagram. To construct the tree diagram, the probababity written on each branch of the tree. The probability of an event for the experiment