Sequence And Series Question 517
Question: If the sum of the 10 terms of an A.P. is 4 times to the sum of its 5 terms, then the ratio of first term and common difference is
[RPET 1986]
Options:
A) $ 1:2 $
B) $ 2:1 $
C) $ 2:3 $
D) $ 3:2 $
Show Answer
Answer:
Correct Answer: A
Solution:
Under conditions, we get $ \frac{10}{2}{ 2a+(10-1)d }=4[ \frac{5}{2}[ 2a+(5-1)d ] ] $
$ \Rightarrow $ $ 2a+9d=4a+8d $ or $ \frac{a}{d}=\frac{1}{2} $ Hence $ a:d=1:2 $ .
BETA
