Sequence And Series Question 509
Question: Let $ S_{n} $ denotes the sum of $ n $ terms of an A.P. If $ S_{2n}=3S_{n} $ , then ratio $ \frac{S_{3n}}{S_{n}}= $
[MNR 1993; UPSEAT 2001]
Options:
A) 4
B) 6
C) 8
D) 10
Show Answer
Answer:
Correct Answer: B
Solution:
$ S_{2n}=3S_{n} $
$ \Rightarrow $ $ \frac{2n}{2}{2a+(2n-1)d}=3\ .\ \frac{n}{2}{2a+(n-1)d} $
$ \Rightarrow $ $ 2a=(n+1)d $ Put $ 2a=(n+1)d $ in $ \frac{S_{3n}}{S_{n}} $ , we get its value 6.
BETA
