JEE Main & Advanced Mathematics Probability Question Bank Definition of probability

  • question_answer
    Consider the circuit,                 If the probability that each switch is closed is p, then find the probability of current flowing through AB [DCE 2005]

    A)                 \[{{p}^{2}}+p\]

    B)                 \[{{p}^{3}}+p-1\]

    C)                 \[{{p}^{3}}+p\]

    D)                 \[{{p}^{2}}+p+1\]

    Correct Answer: A

    Solution :

               Current in the upper part will flow only if both the switches a and b are closed                    \[\therefore \] Their probability = p.p. = \[{{p}^{2}}\]                    Now current will flow in lower part of c, if c is closed, its probability is p. Thus current will flow from A to B if current flows either in upper part or flow in lower part.                                 \ Required probability =\[{{p}^{2}}+p\].


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