ProbabilityProbability or Chance

Probability Aptitude Maths PDF Study Materials

Probability or Chance:

  • Probability or chance is a common term used in day-to-day life. For example, we generally say, ‘it may rain today’. This statement has a certain uncertainty.Probability is quantitative measure of the chance of occurrence of a particular event.


  • An experiment is an operation which can produce well-defined outcomes.

Random Experiment:

If all the possible outcomes of an experiment are known but the exact output cannot be predicted in advance, that experiment is called a random experiment.


  1. Tossing of a fair coin

    When we toss a coin, the outcome will be either Head (H) or Tail (T)

  2. Throwing an unbiased die

    Die is a small cube used in games. It has six faces and each of the six faces shows a different number of dots from 1 to 6. Plural of die is dice.

    When a die is thrown or rolled, the outcome is the number that appears on its upper face and it is a random integer from one to six, each value being equally likely.

  3. Drawing a card from a pack of shuffled cards

    A pack or deck of playing cards has 52 cards which are divided into four categories as given below

    1. Spades (♠)
    2. Clubs (♣)
    3. Hearts (♥)
    4. Diamonds (♦)

    Each of the above mentioned categories has 13 cards, 9 cards numbered from 2 to 10, an Ace, a King, a Queen and a jack

    Hearts and Diamonds are red faced cards whereas Spades and Clubs are black faced cards.

    Kings, Queens and Jacks are called face cards

  4. Taking a ball randomly from a bag containing balls of different colours

Any subset of a Sample Space is an event. Events are generally denoted by capital letters A, B , C, D etc. 
  1. When a coin is tossed, outcome of getting head or tail is an event
  2. When a die is rolled, outcome of getting 1 or 2 or 3 or 4 or 5 or 6 is an event

Simple Events:

In the case of simple events, we take the probability of occurrence of single events.
  1. Probability of getting a Head (H) when a coin is tossed
  2. Probability of getting 1 when a die is throw

Probability PDF Download


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