Sequence And Series Question 555
Question: If the sum of two extreme numbers of an A.P. with four terms is 8 and product of remaining two middle term is 15, then greatest number of the series will be
[Roorkee 1965]
Options:
A) 5
B) 7
C) 9
D) 11
Show Answer
Answer:
Correct Answer: B
Solution:
Let four numbers are $ a-3d,,a-d,\ a+d,\ a+3d $ . Now $ \frac{b}{a}=\frac{d}{c} $
$ \Rightarrow $ $ a=4 $ and $ (a-d)(a+d)=15 $
$ \Rightarrow $ $ a^{2}-d^{2}=15 $
$ \Rightarrow $ $ d=1 $ Thus required numbers are 1, 3, 5, 7. Hence greatest number is 7.
BETA
