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Probability - Theoretical Approach

In our general life we come across the words likely, may be, probably, chance, hope, it may possible e.t.c. All these are synonyms to probability.
The probability that is based on the observations of an experiment is called an experimental or empirical probability. As the number of observations in an experiment increases, the experimental probability gets closer to the theoretical probability.
The results of an experiment are called outcomes.
The possible outcomes of an experiment are called its elementary events.
The sum of the probabilities of elementary events of an experiment is one.
These outcomes are said to be equally likely if each outcome has the same chance of happening.
Events that are mutually exclusive of each other are called complementary events.
The sum of the probabilities of two complementary events is always equal to one.
An event having zero probability of occurrence is called an impossible event.
An event having a probability of 1 is called a sure or certain event.
An event E is a number P(E), such that 0 ≤ P(E) ≤ 1.
The theoretical or classical probability of an event E is denoted by P(E), where

P(E)=