The sum of probabilities of two mutually exclusive events will always be 1.
False
The sum of probabilities of two mutually exclusive events need not be always 1.
For example, consider the events “getting a prime number”, and “getting a composite number” for the experiment of rolling a die. They are mutually exclusive, but the sum of their probabilities is less than 1.
Favorable outcomes for prime no. = 2 , 3, 5
Favorable outcomes for composite no. = 4, 6
P(getting a prime no.) =36=12
P(getting a composite no.) =26=13
12+13≠1. So The sum of probabilities of two mutually exclusive events need not be always 1.