KVPY Sample Paper KVPY Stream-SX Model Paper-5

  • question_answer
    A die is so loaded that the probability of throwing a number is proportional to \[{{K}^{2}}.\] Then the probability that the number 3 appears given that when the die is rolled the number turned up is not even is equal to

    A) \[\frac{9}{70}\]                         

    B) \[\frac{35}{91}\]

    C) \[\frac{9}{91}\]                         

    D) \[\frac{9}{35}\]

    Correct Answer: D

    Solution :

    [d]
    Given, Probability of throwing a number is proportional to \[{{K}^{2}}.\]
    \[\therefore \]\[\sum\limits_{K=1}^{6}{\lambda {{K}^{2}}=1}\] \[\Rightarrow \]\[\frac{\lambda (6)(6+1)(12+1)}{6}=1\]\[\Rightarrow \]\[\lambda =\frac{1}{91}\]
    P [a] = Probability of not getting an even number \[=\lambda ({{1}^{2}}+{{3}^{2}}+{{5}^{2}})\] \[=\lambda \,(35)=\frac{35}{91}\]
    P [b] = Probability of getting 3 \[=\lambda {{(3)}^{2}}=\frac{9}{91}\]
    \[p(B/A)=\frac{(A\cap B)}{P\,(A)}=\frac{P\,(B)}{P\,(A)}\] \[=\frac{9/91}{35/91}=9/35\]


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