Probability


  1. The letters B, G, I, N, R are rearranged to form the word 'BRING'. Find its probability ?









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    The five letters could be arrange in 5! ways.
    One of them is 'BRING'.

    Correct Option: A

    The five letters could be arrange in 5! ways.
    One of them is 'BRING'.
    ∴ Required probability = 1/5!
    = 1/(5 x 4 x 3 x 2 x 1)
    = 1/120


  1. What is the probability that a card drawn at random from a pack of 52 cards is either a king or a spade?









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    Required probability
    = 3/52 + 13/52 = 16/52 =4/13

    Correct Option: B

    Required probability = 3/52 + 13/52 = 16/52 =4/13
    [Hint Why 13/52 because there are 13 spades and why 3/52 instead of 4/52 (there are four kings) because one king is already counted in spades.]



  1. If three unbiased coins are tossed simultaneously, then the probability of exactly two heads, is









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    n(S) = 23 = 8
    Let E = Event of getting exactly two heads
    = {(H, H, T), (H, T ,H), (T, H, H)}

    Correct Option: C

    n(S) = 23 = 8
    Let E = Event of getting exactly two heads
    = {(H, H, T), (H, T ,H), (T, H, H)}
    ⇒ n(E) = 3
    ∴ required probability = 3/8


  1. A card is drawn from a well-shuffled pack of cards. The probability of getting a queen of club or a king of heart is ?









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    Total ways = 52
    There is one queen of club and one king of heart.
    ∴ Favorable ways = 1 + 1 = 2

    Correct Option: B

    Total ways = 52
    There is one queen of club and one king of heart.
    ∴ Favorable ways = 1 + 1 = 2
    ∴ Required probability = 2/52 = 1/26



Direction: Study the information carefully to answer the question that follow.
A basket contains 3 blue, 2 green and 5 red balls.

  1. If three balls are picked at random, what is the probability that atleast one is red ?









  1. View Hint View Answer Discuss in Forum

    Total Number of outcomes = 10C3 = 120
    Number of outcomes not containing red balls = 5C3 = 10
    ∴ Probability that at least one is red = 1 - 10/120

    Correct Option: C

    Total Number of outcomes = 10C3 = 120
    Number of outcomes not containing red balls = 5C3 = 10
    ∴ Probability that at least one is red = 1 - 10/120 = 11/12