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

    Question

    A box contains 13 black and 13 white balls. The

    probability of drawing two balls of the same colour is?   
    A 151/260 Correct Answer Incorrect Answer
    B 145/272 Correct Answer Incorrect Answer
    C 161/292 Correct Answer Incorrect Answer
    D 156/325 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Total number of balls = 13 + 13 = 26 Let S be the sample space. Then, n(S) = number of ways of drawing 2 balls out of 26  =  26C 2 = `(26xx25)/(2xx1)=325` Let E = event of drawing 2 balls of the same color n (E)  =  13C 2 + 13C2 = `(13xx12)/(2xx1)+(13xx12)/(2xx1)`    = 78 +78 = 156  P (E)  =  `(n(E))/(n(S))=156/325`

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