Probability Sample Questions And Answers

Probability Sample Questions And Answers

  • Posted by  Geetha 
    29 Jan, 2012

    Ex 1. In a throw of a coin ,find the probability of getting a head.
    sol. Here s={H,T} and E={H}.

    Ex2.Two unbiased coin are tossed .what is the probability of getting atmost one head?
    sol.Here S={HH,HT,TH,TT}
    Let Ee=event of getting one head

    Ex3.An unbiased die is tossed .find the probability of getting a multiple of 3
    sol. Here S={1,2,3,4,5,6}
    Let E be the event of getting the multiple of 3
    then ,E={3,6}

    Ex4. In a simultaneous throw of pair of dice .find the probability of getting the total more than 7
    sol. Here n(S)=(6*6)=36
    let E=event of getting a total more than 7

    Ex5. A bag contains 6 white and 4 black balls .2 balls are drawn at random. find the probability that they are of same colour.
    Sol .let S be the sample space
    Then n(S)=no of ways of drawing 2 balls out of (6+4)=10c2=(10*9)/(2*1)=45
    Let E=event of getting both balls of same colour
    Then n(E)=no of ways(2 balls out of six) or(2 balls out of 4)

    Ex6.Two dice are thrown together .What is the probability that the sum of the number on the two faces is divided by 4 or 6
    sol. Clearly n(S)=6*6=36
    Let E be the event that the sum of the numbers on the two faces is divided by 4 or 6.Then

    Hence p(e)=n(e)/n(s)=14/36=7/18

    Ex7.Two cards are drawn at random from a pack of 52 cards.what is the probability that either both are black or both are queen?
    sol. We have n(s)=52c2=(52*51)/(2*1)=1326.
    Let A=event of getting both black cards
    B=event of getting both queens
    A∩B=event of getting queen of black cards
    n(B)=4c2=(4*3)/(2*1)=6 and
    P(B)=n(B)/n(S)=6/1326 and

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