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JEE Main & Advanced Mathematics Sequence & Series Question Bank Arithmetic Progression

  • question_answer
    If the sum of the first 2n terms of \[2,\,5,\,8...\] is equal to the sum of the first n terms of \[57,\,59,\,61...\], then n is equal to [IIT Screening 2001]

    A) 10

    B) 12

    C) 11

    D) 13

    Correct Answer: C

    Solution :

    Given,  \[\frac{2n}{2}\{2.2+(2n-1)3\}=\frac{n}{2}\{2.57+(n-1)2\}\] or \[2(6n+1)=112+2n\] or \[10n=110,\,\,\,\,\,\therefore n=11\].


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