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Cinema 2 has 25 seats in the first row and 30 rows in all. Each successive row contains one additional seat. How many seats are in the theater

  • math -

    so you want
    25+26+.. for 30 terms
    an arithmetic series where a=25 , d=1 ,and n=30
    sum(3) = (30/2)(50 + 29(1)) = 1185

  • math -

    a1=25 d=1 n=30

    sn=30/2{2(25)+(30-1)1}
    sn=15(50+29)
    sn=15(79)
    sn=1,185 seats in the theatre

  • math -

    a1=25 d=1 n=30

    sn=30/2{2(25)+(30-1)1}
    sn=15(50+29)
    sn=15(79)
    sn=1,185 seats in the theatre

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