If Sn denote the sum of the first n terms of an A.P. If S2n = 3Sn, then S3n : Sn is equal to
We know that Sn =
Now it is given that
S2n = 3Sn
= 3)
2(2n + 1) = 3(n + 1)
4n + 2 = 3n + 3
n = 1
now, S3n/Sn = ()
=
= 6