## Revision Notes of Chapter 15 Probability Class 9th Math

Topics in the Chapter
• Fundamentals
• Probability
• Complementary Events
• Important Notes for Cards and Probability
Fundamentals

• Experiment: An operation which can produce some well defined outcomes.
• Sample Space: It is the total number of possible outcomes of a random experiment.
• Event: Any subset of a sample space is called a event.
• Elementary Event: Each outcome of any random experiment.
• Sure Event (Certain event): An event which always occurs whenever the random experiment is  performed.
• Impossible Event: An event which never occurs whenever the random experiment is performed.
• Favourable Event: The cases which ensure the occurrence of an event.

Probability

Probability P(E) of an event E is defined as:
P(E) =  Number of favourable outcomes/Total number of outcomes

In short, P(E) =  Favourable Event/Sample Space

Complementary Events

An event associated with a random experiment denoted by (not E) which happens only when E does  not happen is called the complement of event E.

P(not E) = 1 – P(E)

Important Note
1. Sum of the probabilities of all the elementary events of an experiment is 1.
P(E1) + P(E2) + P(E3) + ..................... + P(En) = 1
2. Probability of Sure Event is 1.
3. Probability of an Impossible Event is 0.
4. Probability of any event lies between 0 and 1 (including 0 and 1) i.e. 0 ≤ P(E) ≤ 1.
5. 52 cards are divided into 4 suits of 13 cards each.The suits are: 