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JEE Main & Advanced Mathematics Permutations and Combinations Question Bank Self Evaluation Test - Permutations and Combinatioins

  • question_answer
    Let \[A=\{x|x\] is prime number and\[x<30\}\]. The number of different rational numbers whose numerator and denominator belong to A is

    A) 90

    B) 180

    C) 91

    D) 100

    Correct Answer: C

    Solution :

    [c] We have \[A=\{2,3,5,7,11,13,17,19,23,29\}\] A contains 10 elements. So numerator and denominator each can be chosen in 10 ways. So no. of rational numbers \[=10\times 10-10+1=91\] (Out of these selections, 10 numbers are simply 1)


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