Sequence And Series Question 224
Question: The sum of a G.P. with common ratio 3 is 364, and last term is 243, then the number of terms is
[MP PET 2003]
Options:
A) 6
B) 5
C) 4
D) 10
Show Answer
Answer:
Correct Answer: A
Solution:
$ \frac{ar^{n}-a}{r-1}=364 $
$ \Rightarrow \frac{a{r^{n-1}}.r-a}{r-1}=364 $ ?..(i)
Þ $ \frac{3\times 243-a}{2}=364 $
$ \Rightarrow a=1 $ Now, putting this in (i), n = 6.
BETA
