Probability is the ratio of the number of possible outcome to the number of total outcome.
The probability that an event will happen added to the probability that the event will not happen gives 1. In other words, the outcome of a probability cannot exceed 1.
The probability that an event a will happen or that another independent event b will happen is the sum of the probability that a will happen to the probability that b will happen.
The probability that the event B will occur 3 times in a row may be interpreted as BBB and in probability, "and" is interpreted as multiplication while "or" is addition.
