JEE Main & Advanced JEE Main Paper Phase-I (Held on 07-1-2020 Evening)

  • question_answer
    If the sum of the first 40 terms of the series, \[3+4+8+9+13+14+18+19+\]... is (102)m, then m is equal to                                                                              [JEE MAIN Held on 07-01-2020 Evening]

    A) 5                     

    B) 20

    C) 25       

    D) 10

    Correct Answer: B

    Solution :

    [b] \[S\text{ }=\text{ }3+4+8+9+13+14+18+\,...40\]terms. \[=7+17+27+\text{ }...\text{ }20\]terms \[=\frac{20}{2}\{2\times 7+(20-1).10\}\] \[=\,2040\] \[(102)m=2040\] \[\therefore \,\,\,m=20\]

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