10th Class Mathematics Related to Competitive Exam Question Bank Algebra

  • question_answer
    The product\[\left( 1-\frac{1}{n} \right)\left( 1-\frac{1}{n+1} \right)\left( 1-\frac{1}{n+2} \right)......\left( 1-\frac{1}{2n} \right)\] equals

    A)  \[\frac{n-1}{2n}\]             

    B)         \[\frac{1}{2n}\]

    C)  \[\frac{2n}{n-1}\]           

    D)         \[\frac{1}{n}\]

    Correct Answer: A

    Solution :

     Given product \[=\left( 1-\frac{1}{n} \right)\left( 1-\frac{1}{n+1} \right)\left( 1-\frac{1}{n+2} \right)...\left( 1-\frac{1}{2n} \right)\] \[=\frac{(n-1)}{n}\times \frac{n}{(n+1)}\times \frac{n+1}{(n+2)}...\left( \frac{2n-1}{2n} \right)\] \[=\frac{(n-1)}{2n}\]


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