Which of the following geometric progressions has the common ratio as √2?
Which of the following geometric progressions has the common ratio as √2?
A) √2 , √6 , \(\sqrt{18}\),..............
B) √3, √6, \(\sqrt{12}\),...........
C) √5, \(\sqrt{15}\) ,\(\sqrt{45}\) ,..........
D) √7 , \(\sqrt{21}\) , \(\sqrt{63}\),..........
2 Answers
Correct option is (B) \(\sqrt3 ,\sqrt6 ,\sqrt{12} ,......\)
In a G.P. common ratio is \(r=\frac{a_2}{a_1}\)
(A) \(\sqrt2 ,\sqrt6 ,\sqrt{18} ,......\)
\(r=\frac{a_2}{a_1}=\frac{\sqrt6}{\sqrt2}\)
\(=\frac{\sqrt3.\sqrt2}{\sqrt2}=\sqrt3\)
(B) \(\sqrt3 ,\sqrt6 ,\sqrt{12} ,......\)
\(r=\frac{\sqrt6}{\sqrt3}\)
\(=\frac{\sqrt3.\sqrt2}{\sqrt3}=\sqrt2\)
(C) \(\sqrt5 ,\sqrt{15} ,\sqrt{45} ,......\)
\(r=\frac{a_2}{a_1}=\frac{\sqrt{15}}{\sqrt5}\)
\(=\frac{\sqrt3.\sqrt5}{\sqrt5}=\sqrt3\)
(D) \(\sqrt7 ,\sqrt{21} ,\sqrt{63} ,......\)
\(r=\frac{a_2}{a_1}=\frac{\sqrt{21}}{\sqrt7}\)
\(=\frac{\sqrt7.\sqrt3}{\sqrt7}=\sqrt3\)