10_Answer sheet of A.P. U-5 Part-3

11.  n = 30th
12.  a= -13, d = 5, a(1)= -13, a(2)= -8
        a(3) = -3
13.  a(12)= 38
14.  S(10)= -80
15.  n= 54th, S(54)= 32373