Sequence And Series Question 201
Question: The first term of a G.P. is 7, the last term is 448 and sum of all terms is 889, then the common ratio is
[MP PET 2003]
Options:
A) 5
B) 4
C) 3
D) 2
Show Answer
Answer:
Correct Answer: D
Solution:
$ a=7anda{r^{n-1}}=448 $ Now, $ S_{n}=\frac{a(r^{n}-1)}{r-1}=889 $
$ \Rightarrow \frac{(a{r^{n-1}}.r-a)}{r-1}=889 $
Þ $ \frac{448r-7}{r-1}=889 $
Þ $ r=2 $ .
BETA
