Calculate the error!

The time $T$ of a complete oscillation of a simple pendulum of length $l$ is given by:

$T =2\pi \sqrt { \dfrac { l }{ g } }$

where $g$ is a constant.

Find the approximate error in the calculated value of $T$ corresponding to an error of $2\%$ in the value of $l$

The answer is $x\%$

Find $x$