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SSC Sample Paper Mock Test-3 SSC CGL Tear-II Paper-1

  • question_answer
    Find the sum of 20 terms of an AP whose first term is 4and common difference is 3.

    A)  550                             

    B)  650

    C)  750                             

    D)  None of these

    Correct Answer: B

    Solution :

    Here, a = 4, d = 3, n = 20 so, \[{{S}_{20}}=\frac{20}{2}[2\,\,(4)+19\times 3]=10\,\,[8+57]=650\] If first term \[=a\] and last term \[={{a}_{n}}\] are given, then sum of terms of an AP is \[{{S}_{n}}=\frac{n\,\,({{a}_{1}}+{{a}_{n}})}{2}\] where,         n = number of terms.


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