Q. 155.0( 8 Votes )

If Sn denote the sum of the first n terms of an A.P. If S2n = 3Sn, then S3n : Sn is equal to
A. 4

B. 6

C. 8

D. 10

Answer :

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

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