10_Answer sheet of A.P. U-5 Part-2

6. S(11)= 1683
7. n= 15th, S(15)= 810
8. a(10)= 47
9. a= 6, d=4, a(100)= 402,
    S(50)= 5200
10. a(21)= 3 x a(11)