MCQ
Three positive numbers form an increasing $G.P.$ If the middle term in this $G.P.$ is doubled, the new numbers are in $A.P.$ then the common ratio of the $G.P.$ is:
  • A
    $2 - \sqrt 3 $
  • $2 + \surd 3$
  • C
    $\sqrt 2 + \surd 3$
  • D
    $3 + \surd 2$

Answer

Correct option: B.
$2 + \surd 3$
b
Let the numbers be $a, a r, a r^{2}$

If $a r$ is doubled then,

$\Longrightarrow 2 a r=\frac{a r^{2}+a}{2}$

$\Longrightarrow 4 a r=a r^{2}+a$

$\Longrightarrow 4 r=r^{2}+1$

$\Longrightarrow r^{2}-4 r+1$

On solving we get

$r=2 \pm \sqrt{3}$

since it is an increasing

$G . P^{\prime} r^{\prime}=2+\sqrt{3}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free