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CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2010

  • question_answer
    An AP consists of 23 terms. If the sum of the three terms in the middle is 141 and the sum of the last three terms is 261, then the first term is

    A)  6                                            

    B)  5

    C)  4                            

    D)         3

    E)  2

    Correct Answer: D

    Solution :

    Let a be first term and d be common difference of AP. Then, according to question          \[(11th+12th+13th)term=141\] \[\Rightarrow \]\[a+10d+a+11d+a+12d=141\] \[\Rightarrow \]\[3a+33d\,=141\]                            ?(i) and\[(21th+22th+23th)term=261\] \[\Rightarrow \]\[a+20d+a+21d+a+22d=261\] \[\Rightarrow \]               \[3a+63d=261\]                ? (ii)      Solving Eqs. (i) and (ii), we get \[a=3,\text{ }d=4\] \[\therefore \]  First term = 3


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