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Probability Class 9 Notes CBSE Maths Chapter 15 (Free PDF Download)

Last updated date: 26th Nov 2023
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MVSAT Dec 2023

Class 9 Maths Revision Notes for Probability of Chapter 15 - Free PDF Download

The Class 9 Maths revision notes chapter 15 Probability are available on Vedantu in PDF format. Probability is simply an event of uncertainty. It is a way to measure the uncertainty of any ambiguous situation. In mathematics, Probability is considered as an experimental approach and an outcome of probability based on the actual experiments— known as the Empirical Probability. Probability is dependent upon the number of trials and the number of times the desired event takes place. Download and refer to the Class 9 revision notes maths ch 15 for free from Vedantu for a better understanding of the concepts.

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Class 9 Maths Revision Notes Chapter 15 Probability

Probability Formula

Suppose the total number of trials is ‘n’ then the probability of an event (D) occurring will be: P (D) = number of trials in which the event occurred/ total number of trials.

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

Here, you will get the requisite definition, concepts, and problems on the concepts of probability. Below are some of the important topics you will need to cover from class 9 maths notes of probability.

Uses And Application of Probability

Probability is widely used in various fields, such as, Physical Sciences, Medical Sciences, Biological Sciences, Commerce, Weather Forecasting, Mathematics, etc.

Standard Terms Related To Probability

  1. Randomness

If we are conducting an experiment and we are not aware of the next result of the experiment to happen then it is known as the Random Experiment.

  1. Trial

A trial is that action whose result is not just one but there may be one or more results. For example, pull the card of spade 7 from the deck of cards or the outcome of a throw of a dice, etc.

  1. Independent Trial

A trial is said to be independent if it does not affect the result of any other random trial. Like tossing a coin or throwing a dice are independent trials as they are not bound to impact each other.

  1. Event

While performing an experiment, an event will be the gathering of some results of that experiment. For example, when we throw a dice, then the possibility of having an outcome of an odd number will be three, i.e., 1, 3, 5. So the event would comprise of three outcomes.

  1. Impossible Events

While performing a test if an event is not possible to take place then its probability will be zero (0). This is called an Impossible Event. For example, you cannot throw dice with the outcome of number eight on it. Thus, the probability of getting an 8 on dice is 0%.

  1. Sure or Certain Event

While carrying out a test if there is a certainty of an event to take place, then it is said to be a certain probability. Here the probability is 1. For example, it is sure to draw a red ball from a bag that contains red balls only.

This proves that the probability of an event could be between 1 and 0. Thus, 0 ≤ P (E) ≤ 1.

  1. Elementary Event

If there is only one possible outcome of an event to take place, then it is what we call an Elementary Event. For example, if we add all the elementary events of an experiment then their sum will be 1.

The general form is as given:

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 Maths Chapter 15

You will find the following types of problems on probability in your Maths Class 9 Probability Notes.

Example 1

If a coin is tossed 200 times out of which 70 times we get heads and 130 times we get tails. Then,

  1. Find the probability of getting a heads.

  2. Find the probability of getting a tail.

  3. Check if the sum of the two probabilities is equivalent to 1 or not.

Solution 1

a. Let the probability of getting a heads on the coin be P (H)

Thus, applying the formula:

P (H) = number of trials in which the head comes/ total number of trials

= 70/200


b. Let the probability of getting a heads on the coin be P (T)

Thus, applying the formula:

P (T) = number of trials in which the tail comes/ total number of trials

= 130/200


c. The sum of 2 probability will be = P(H) + P(T)

= 70/200 + 130/200 = 200/200 = 1

FAQs on Probability Class 9 Notes CBSE Maths Chapter 15 (Free PDF Download)

1. How are notes of class 9 revision notes chapter 15 beneficial for students?

Revision is of utmost importance in order to gain better conceptual understanding and obtaining good marks. For revision, quick notes are always considered the best. Probability class 9 revision notes formulated by the expert teachers at Vedantu can prove to be very beneficial for students for the purpose of revising all their previously prepared units and concepts, particularly during examination times when they need to revise the whole syllabus in a limited time frame.

2. Is class 9 revision notes maths ch 15 available online for free?

Vedantu offers the best CBSE revision notes class 9 maths chapter 15 for free. Students get the privilege to prepare Chapter 15 Revision Notes provided by Subject Matter Experts at Vedantu who possess extensive experience in teaching.

3. Is it important for CBSE students to refer to ch 15 class 9 maths revision notes?

It is not about importance but the valued possession of these notes for students.  CBSE Class Revision Notes are one of the most helpful study materials that students would get as these will facilitate them to prepare the chapter better and address their doubts from the chapter more effectively.

4. What is the meaning of probability according to NCERT Solutions for Class 9 Maths Chapter 15?

NCERT Solutions are specially designed study materials for guiding students in an easy and understandable manner. For the chapter on Probability, these solutions define the term as the measure of an event that is likely to occur, that is, a chance or likelihood of an event occurring is what is termed as 'probability'. The range lies in between the values of 0 and 1 with a percentage value between 0% and 100%. The Solutions are available on the vedantu website and the vedantu app.

5. What are the benefits of using revision notes for the chapter on ‘Probability’ for class 9?

'Probability' is a chapter of chances and likelihoods and students can easily understand the concepts through the short and accurate Notes that can be used as an excellent reference and last-minute guide. These topics cover all the crucial topics that students need from this chapter by giving them an opportunity for rounds of revisions quickly before their exams. These are exclusively prepared by expert teachers so that students can trust in their content and study well for their exams. Students can also download the revision notes free of cost from the website (

6. What are the important formulae used in the chapter of ‘Probability’ for Class 9?

The chapter on Probability has only one basic important formula that students need to remember throughout the chapter. CBSE Notes is a fine study material that helps students organize their study time and concepts. The formula is stated below along with some basic formulas:

  • Probability of event that is likely to happen, 

P(E) = No: of favourable outcomes of the event(r)/Total no. of outcomes of the event(n)

  • P(E) = r/n

  • P(E’) = (n-r)/n = 1-(r/n)

  • P(E) + P(E’) = 1

7. What are the important concepts covered in the NCERT Solutions for Class 9 Maths Chapter15?

Chapter 15 deals with topics and concepts revolving around Probability. CBSE Notes cover each and every topic in detail starting with the definition of probability and then ending in different events likely to occur. The following concepts are prepared in short and precise words for easy comprehension:

  • Probability

  • Experiment and Trial

  • Experimental Probability

  • Coin Tossing Experiment

  • Dice Roll Experiment

Sum probabilities of both favourable and unfavourable events. These important topics are covered in the notes which can be accessed from the vedantu website (

8. How do I solve the questions of class 9 Maths, Chapter 15?

In Class 9, students learn Probability in chapter 15 of their textbooks. Probability is relatively an easy chapter when compared with the bulk of chapters in the textbook, and CBSE Notes can make this chapter even easier through its short and precise factual explanation of concepts. The formula

P( E )= No: of favourable outcomes of the event/ Total no: of outcomes of the event 

is all the students need to solve the different questions asked from the chapter.