RS Aggarwal Solutions for Class 7 Chapter 23 Probability- It is a number that reflects a chance or likelihood that a particular event will occur. A probability is a real number between 0 and 1 that describes how likely it is that an event will occur. A probability of 0 means that an event will never occur. A probability of 1 means that an event will always occur. A probability of 0,5 implies that an event will occur half the time or 1 time out of every 2. The words ‘most probably’, ‘chance’, doubt, etc., indicate uncertainty or probability of occurrence of an event. Though probability started with gambling, it is now used extensively in diverse fields such as commerce, biological science, weather forecasting, etc.