The volume of a cone is:

$V = \frac{1}{3}\pi r^2 h$

Substitute $V = 616$ and $h = 5$:

$616 = \frac{1}{3}\pi r^2 (5)$

$616 = \frac{5\pi r^2}{3}$

Solve for $r^2$:

$r^2 = \frac{616 \times 3}{5\pi} = \frac{1,848}{5\pi}$

Take the square root:

$r = \sqrt{\frac{616(3)}{5\pi}}$