Radical Equation Word Problems - Examples & Practice

Astronaut Kevin discovered the planet Beyoncionia. He found out that the formula $T=2\pi\sqrt{\frac{L}{28}}$ represents the swing of a pendulum on the planet. $T$ is the time in seconds it takes to swing back and forth, and $L$ is the length of the pendulum in feet. Find the length of a pendulum that makes one swing in $4.2$ seconds. Round your answer to the nearest hundredth.