Probability:

Refer below points for to understand probability concept.

Probability is defined as feasibility of happening an event. In other way also we can defined as below.

The possibility of happening or not happening of an event is known as probability.

Possibility of happening of an event = (Number of favourable outcomes / Total number of outcomes)

Experiment: It is an action where result is uncertain

Sample space: It is set of all the possible outcomes of that experiment. Denoted by ‘S’

Example: If we toss a coin, sample space = {Head, Tail}

Event: Event is the result of an experiment

Mutually Exclusive Events: Two events are called mutually exclusive events when they cannot occur at the same time.

Dependent Events: Two events are called Dependent events when the outcome of the first event should affect the outcome of second event.

Independent Events: Two events are called Independent events when the outcome of the first event should not affect the outcome of second event.

Previous year solved Questions:

Study the given information carefully and answer the following questions.

A basket contains 4 red, 5 blue and 3 green marbles.

1. If two marbles are drawn at random, what is the probability that both are red?

A) 3 / 7 B) 1 / 2 C) 2 / 11 D) 1 / 6 E) None of these

Ans: E

Solution: According to the formulae,

=> Possibility of happening of an event = (Number of favourable outcomes / Total number of outcomes)

=> (4c2 / 12c2) = (6/66) = (1 / 11)

2. If three marbles are picked at random, what is the probability that at least one is blue?

A) 7 / 12 B) 37 / 44 C) 5 / 12 D) 7 / 44 E) None of these

Ans: B

Solution: As per given data, total number of possible outcomes = 12c3 = 220

=> Number of events that do not contain blue marbles = 7c3 = 35

=> Probability = [1 – (35/220)] = 37/44