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

  • question_answer
    If the sum of three consecutive terms of an A.P. is 51 and the product of last and first term is 273, then the numbers are [MP PET 1986]

    A) 21, 17, 13

    B) 20,16, 12

    C) 22, 18, 14

    D) 24, 20, 16

    Correct Answer: A

    Solution :

    Let consecutive terms of an A.P. are \[a-d,\ a,\ a+d\]. Under given condition, \[(a-d)+a+(a+d)=51\] \[\Rightarrow \] \[a=17\] and \[(a-d)(a+d)=273\]\[\Rightarrow \]\[{{a}^{2}}-{{d}^{2}}=273\] \[\Rightarrow \] \[-{{d}^{2}}=273-289\]\[\Rightarrow \]\[d=4\] Hence consecutive terms are 13, 17, 21. Trick: Both conditions are satisfied by (a) \[i.e.\] 21, 17, 13.


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