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

    Question

    There are 30 cars standing in a parking lot which

    consist of silver, grey and white cars. The number of grey and white cars are equal, and the number of silver cars is 3 more than the number of white cars. If 3 cars are randomly selected, what is the probability that at least one of them is silver?
    A 943/1123 Correct Answer Incorrect Answer
    B 1391/1595 Correct Answer Incorrect Answer
    C 211/523 Correct Answer Incorrect Answer
    D 11/52 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the number of grey and white cars be ’x’ each. Then the number of silver cars will be ‘x + 3’. So, (x + 3) + x + x = 30 3x = 27 x = 9 So, number of silver, grey and white cars is 12, 9 and 9 respectively. Required probability = P (at least one of them is silver) = 1 – P (none of them is silver) = 1 – (18/30) × (17/29) × (16/28) = 1 – (204/1595) = (1391/1595)

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