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For the arithmetic series 13+19+...

a. find tsub27
b. find Ssub27
c. if tsubn = 445, find n

  • math -

    a=13
    d=6
    T27 = 13+26*6 = 169
    S27 = 27/2 (2*13 + 26*6) = 2457

    445 = 13 + (n-1)6
    n=73

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