Question

a fair coin is toss 3 times. find the probability of 
1. All the tosses obtain heads.
2. number of heads of heads obtained is one(1)

Answer 1

probability of all heads = 1/2 *1/2 *1/2
                                 =1/8
probability of one head = prob of (H T T + T H T + T T H)
                                  = three combinations out of all possible combinations (8)
                                  = 3/8