RS Aggarwal Solutions for Class 9 Chapter 19 “Probability”, Probability is the branch of mathematics concerning numerical descriptions of how likely an event is to occur, or how likely it is that a proposition is true. The Probability of an event is a number between 0 and 1, where, roughly speaking, 0 indicates impossibility of the event and 1 indicates certainty. Probability = the number of ways of achieving success. The total number of possible outcomes. For example, the probability of flipping a coin and it being heads is ½, because there is one way of getting a head and the total number of possible outcomes is 2 (a head or tail). We write P (heads) = ½. Some of the significant applications of Probability are sports strategies, forecasts, games and recreational activities, insurance options and in business.