New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    22 defective pens are accidentally mixed with 136 good

    ones. It is not possible to just look at a pen and tell whether or not it is defective. One pen is taken out at random from this lot. Determine the probability that the pen is taken out is a good one.
    A 0.865 Correct Answer Incorrect Answer
    B 0.870 Correct Answer Incorrect Answer
    C 0.860 Correct Answer Incorrect Answer
    D 0.877 Correct Answer Incorrect Answer

    Solution

    Numbers of pens = Numbers of defective pens + Numbers of good pens ∴ Total number of pens = 136 + 22 = 158 pens P(E) = (Number of favourable outcomes) / (Total number of outcomes) P(picking a good pen) = 136/158 = 0.860

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