11th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-7

  • question_answer
    The middle term in the expansion is \[{{\left( \frac{2{{x}^{2}}}{3}+\frac{3}{2{{x}^{2}}} \right)}^{10}}\]is:

    A)  252                 

    B)  352          

    C)  452                             

    D)  250

    Correct Answer: A

    Solution :

    [a] Here, \[n=10=\]even number Here, no. of terms in the expresion be \[n+1\,i.e.11\] i.e. It has single middle terms. So, 6th be the middle terms \[\therefore \] Middle term in the expansion \[{{\left( \frac{2{{x}^{2}}}{3}+\frac{3}{2{{x}^{2}}} \right)}^{10}}{{=}^{10}}{{C}_{5}}.\left( \frac{2{{x}^{3}}}{3} \right).{{\left( \frac{3}{2{{x}^{2}}} \right)}^{5}}\] \[{{=}^{10}}{{C}_{5}}=\frac{10\times 9\times 8\times 7\times 6}{5\times 4\times 3\times 2}\] \[=9\times 4\times 7=252\] Hence option [a] is correct.


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