#### Answer

$r_{1}/r_{2} =\sqrt {10}/2$

#### Work Step by Step

$r_{1}/r_{2} =\sqrt {m_{2}}/\sqrt {m_{1}}$
$r_{1}/r_{2} =\sqrt {30}/\sqrt {12}$
$r_{1}/r_{2} =\sqrt {30}*\sqrt {12}/\sqrt {12}*\sqrt {12}$
$r_{1}/r_{2} =\sqrt {360}/12$
$r_{1}/r_{2} =\sqrt {6*6*10}/12$
$r_{1}/r_{2} =6*\sqrt {10}/12$
$r_{1}/r_{2} =6/12 * \sqrt {10}$
$r_{1}/r_{2} =1/2 * \sqrt {10}$
$r_{1}/r_{2} =\sqrt {10}/2$