A complement of an event is denoted as P(A is the event of choosing every number that is NOT negative i.e., 0,1,2 & 3 (0 is neither positive or negative).What is the probability of the occurrence of a number that is odd or less than 5 when a fair die is rolled. What is the probability of choosing 2 chocobars and 1 icecream?Solution Let the event of the occurrence of a number that is odd be ‘A’ and the event of the occurrence of a number that is less than 5 be ‘B’. P(A) = 3/6 (odd numbers = 1,3 and 5) P(B) = 4/6 (numbers less than 5 = 1,2,3 and 4) P(A and B) = 2/6 (numbers that are both odd and less than 5 = 1 and 3) Now, P(A or B) = P(A) P(B) – P(A or B) = 3/6 4/6 – 2/6 P(A or B) = 5/6. Solution Probability of choosing 1 chocobar = 4/8 = 1/2 After taking out 1 chocobar, the total number is 7.This is depicted as follows: 0 Another example is the rolling of dice. What is the probability of rolling a 5 when a die is rolled? Compound probability is when the problem statement asks for the likelihood of the occurrence of more than one outcome. P(A or B) is the probability of the occurrence of atleast one of the events.P(A and B) is the probability of the occurrence of both A and B at the same time.In mathematics too, probability indicates the same – the likelihood of the occurrence of an event.Examples of events can be : Either an event will occur for sure, or not occur at all.Understanding the basic rules and formulas of probability will help you score high in the entrance exams.As the Oxford dictionary states it, Probability means ‘The extent to which something is probable; the likelihood of something happening or being the case’.An event that doesn’t occur at all is called an impossible event and its probability is 0.This means that all other possibilities of an event occurrence lie between 0 and 1. of possible outcomes = 6 So the probability of rolling a particular number when a die is rolled = 1/6.