CBSE Class 9 Maths Revision Notes Chapter 15

Class 9 Mathematics Chapter 15 Notes

Class 9 Mathematics Revision Notes for Probability of Chapter 15

Probability refers to the likelihood or chances of an event occurring in an uncertain situation. It is a method used to gauge the degree of ambiguity in any given circumstance. Probability is regarded in mathematics as an experimental approach and a result of probability based on actual experiments; this is known as empirical probability. The number of trials and the frequency with which the desired event occurs affect probability. To better understand these concepts, access the Class 9 Mathematics Chapter 15 Notes from Extramarks.

Class 9 Mathematics Revision Notes for Probability of Chapter 15

Class 9 Mathematics Revision Notes Chapter 15 Probability

Probability Formula

If there are n trials total, then the probability that an event (D) will occur is given by: P (D) = number of trials where the event occurred/number of trials overall.

Summary of Notes of Class 9 Revision Notes Chapter 15- Probability

The key points from the probability notes for Class 9 Mathematics Chapter 15 are listed below.

Uses and Application of Probability

Numerous fields, including the physical sciences, medical sciences, biological sciences, commerce, weather forecasting, mathematics, etc., heavily rely on probability.

Standard Terms Related to Probability


The term “random experiment” refers to a procedure of experimentation where the outcome is unknown.


A trial is an action with potential outcomes that may include more than one. Take the spade card number seven out of the deck, for instance, or the result of a dice throw, etc.

Independent Trial

If the outcome of one random trial has no bearing on the outcome of another, the trial is said to be independent. Like flipping a coin or rolling a die, these actions are independent trials because they cannot possibly affect one another.


The gathering of some experimental results will occur as the experiment is being conducted. When we roll the dice, for instance, the likelihood of getting an odd number, such as 1, 3, or 5, is three. The event would then have three possible outcomes.

Impossible Events

While performing a test, if it is not possible for an event to take place, then its probability will be zero (0). The term “impossible event” refers to this. One cannot, for instance, throw a dice with the outcome of 8, for example. Therefore, there is no chance of rolling an 8 on the dice.

Sure or Certain Event

If an event is certain to occur during the course of a test, it is referred to as having a certain probability. Here, the likelihood is 1. For instance, if a bag only contains red balls, it is guaranteed that a red ball will be drawn from it.

This demonstrates that an event could have a probability of between 1 and 0. Thus, 0 ≤ P (E) ≤ 1.

Elementary Event

An event is known as an elementary event if there is only one possible outcome. For instance, if all of an experiment’s fundamental events are added, their total will equal 1.

The basic form is as follows:

P (H) + P (T) = 1

P (H) + P= 1 (where H- ‘not H’).

P (H) – 1 = P

P (H) and P are called complementary events.

Solved Examples Included In Revision Notes Class 9 Mathematics Chapter 15

FAQs (Frequently Asked Questions)

1. How can students benefit from Chapter 15 Mathematics Class 9 Notes?

It is crucial to revise to improve conceptual understanding and score well in exams. Revision notes are always preferred for a quick overview of the chapter. In order to review all of their previously prepared units and concepts, students may find the Probability Chapter 15 Mathematics Class 9 Notes created by subject matter experts to be very helpful. This is especially true during exam times when students must review the entire syllabus.

2. What key ideas are covered in Class 9 Mathematics Chapter 15 Notes?

Class 9 Chapter 15 Mathematics Notes have brief points for all the topics under probability. The CBSE Notes go into great detail on each concept, beginning with the definition of probability and concluding with various events that are likely to occur. The topics covered include:

  • Probability
  • Experiment and Trial
  • Experimental Probability
  • Coin Tossing Experiment
  • Dice Roll Experiment

Add up the odds of both favourable and unfavourable scenarios. The notes, which are accessible from the Extramarks, cover these crucial subjects.

3. What are the advantages of using the Class 9 Mathematics Chapter 15 Notes for the chapter on "Probability"?

Students can easily understand the concepts in the chapter “Probability,” which is about chance and likelihood, thanks to the concise and accurate Class 9 Mathematics Chapter 15 Notes, which make great reference material for revisions. Students quickly go over any important material before their exams while covering all the material they need to know from this chapter with these notes. They are created by subject matter experts, giving students the confidence they need to understand the material and prepare effectively for exams. Students can easily access the revision materials from the Extramarks.