Sequence And Series Question 434
Question: If the product of three consecutive terms of G.P. is 216 and the sum of product of pair-wise is 156, then the numbers will be
[MNR 1978]
Options:
A) 1, 3, 9
B) 2, 6, 18
C) 3, 9, 27
D) 2, 4, 8
Show Answer
Answer:
Correct Answer: B
Solution:
Let numbers are $ \frac{a}{r},\ a,\ ar $ Under conditions, we get $ \frac{a}{r}\ .\ a\ .\ ar=216 $
$ \Rightarrow $ $ a=6 $ And sum of product pair wise $ =156 $
$ \Rightarrow $ $ \frac{a}{r}\ .\ a+\frac{a}{r}\ .\ ar+a\ .\ ar=156 $
$ \Rightarrow $ $ r=3 $ Hence numbers are 2, 6, 18. Trick: Since $ 2\times 6\times 18=216 $ (as given) and no other option gives the value.
BETA
