Krishna
1

Step 1: Analyse the given question and identify the given event.

Mutually exclusive events: If a coin is tossed, we get head or tail, but not both. Similarly, if we select a student of a high

school that student may belong to one of either 6, 7, 8, 9 or 10 class, but not to any two or more classes. In both these

examples, occurrence of an event prevents the occurrence of other events. Such events are called mutually exclusive events.

Elementary event:  An event having only one outcome in an experiment is called an elementary event.

EXAMPLE:  Find the probability of getting a head when a coin is tossed

once. Also find the probability of getting a tail.

Complimentary events: Two events are said to be complementary when one event occurs if and only if the other does not. The

probabilities of two complimentary events add up to 1.

EXAMPLE: Rolling a die and getting a 1 or not-a-1 are complementary

(you have to roll either a 1 or not-a-1).

• This is like flipping a coin and getting heads or tails. Of course, there are no    other options, so these events are complementary.

• Rolling a die and getting a 1 or 2 are not complementary since there are other outcomes that may happen (3, 4, 5, or 6).

Therefor the given events are complementary events because, if one event happens there is no chance the other can.

P(E) + P(\bar{E}) = 1