Revision Notes of Chapter 15 Probability Class 9th Math

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

    • 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 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:
      Spade, Hearts, Diamonds and Clubs
    6. Out of 52 cards, 26 are red in colour and 26 are black in colour.
    7. In each suit, there is an Ace, a King, a Queen, a Jack, 10, 9, 8, 7, 6, 5, 4, 3 and 2.
    8. King, Queen and Jack are called Face cards.

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