Step 1:  Find the total number of possible out comes.

             NOTE:  In the experiment of tossing a coin once, the number of possible

                          outcomes is two - Head (H) and Tail (T).


Step 2:  Find the number of out comes favorable.

                Let E be the event 'getting a head'.

            The number of outcomes favourable to E, (i.e., of getting a head) is 1.

Step 3: Calculate the probability

               Therefore, P(E) = P (head) =\frac{\text{Number of outcomes favourable to E}}{\text{Number of all possible outcomes}}

                     P(E) = \frac{1}{2}

        Similarly, if F is the event 'getting a tail',

           then, P(F) = P(tail) = \frac{1}{2}