Question

Choose Correct Alternative.

1) In an A.P. if a= 10,tn = 20; Sn=120 then n=..........?
A) 5
B) 3
C) 8
D) 12​

Answer 1

Sn = n/2 ( a+ l)

120= n/2(10+20)

120= n *15

n =120/15

n=8

Answer 2

Answer:

I hope so it will be help you