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11th Class Mathematics Sequence and Series Question Bank Sequence and Series (A.P., G.P. and H.P.)

  • question_answer
    In the series, \[{{T}_{n}}=2n+5\], find \[{{S}_{4}}\].

    A)  20                               

    B)  40   

    C)  60                               

    D)  80

    Correct Answer: B

    Solution :

    (b): \[{{T}_{n}}=2n+5;\,\,{{T}_{1}}=2(1)+5=7\]; \[{{T}_{2}}=2(2)+5=9;\,\,{{T}_{3}}=2(3)+5=11\]; \[{{T}_{4}}=2(4)+5=13\] \[{{S}_{4}}={{T}_{1}}+{{T}_{2}}+{{T}_{3}}+{{T}_{4}}=7+9+11+13=40\].          


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