Subject

    Quantitative Aptitude

    Topic

    Probability

    A factory produces four different types of products, P, Q, R and S. The chances that a random piece of products P, Q, R and S is found to be defective are 20%, 30%, 5% and 10%, respectively. During an inspection, one piece of each product is randomly selected. What is the probability that exactly three of them are found to be defective?

    ক)
    0.005
    খ)
    0.0103
    গ)
    0.0124
    ঘ)
    0.0057
    ঙ)
    0.0178

    Explanation

    The chances that a random piece of products P, Q, R and S is found to be defective are 20%, 30%, 5% and 10%, respectively. In terms of probability, this can be stated as probability that a random piece of products P, Q, R and S is found to be defective are 0.20, 0.30, 0.05 and 0.10, respectively. There can be four cases when exactly three of chosen pieces are defective. Case i) Only P, Q and R are defective Probability = 0.2 × 0.3 × 0.05 × (1-0.1) = 0.0027 Case ii) Only P, Q and S are defective Probability = 0.2 × 0.3 × (1-0.05) × 0.1 = 0.0057 Case iii) Only P, R and S are defective Probability = 0.2 × (1-0.3) × 0.05 × 0.1 = 0.0007 Case iv) Only Q, R and S are defective Probability = (1-0.2) × 0.3 × 0.05 × 0.1 = 0.0012 ∴ Probability that exactly three of them are found to be defective = 0.0103

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