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10th Class Mathematics Arithmetic Progressions Question Bank Arithmetic Progressions

  • question_answer
    Find the value of 'n' if the sum of the first 'n' terms of the A.P.I 5, 23, 31, ....... is 708.

    A)  9                            

    B)         8

    C)  12                         

    D)         10

    Correct Answer: C

    Solution :

     \[=\frac{6m}{{{m}^{2}}+9}\] \['x'\] \[1441\times x=5040\times 12\] \[\Rightarrow \] \[x=\frac{5040\times 12}{144}=420\]or \[219\times =657\] Hence, the number of terms is n = 12.


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