The variance of the distribution $=npq$, where, $n$ is the number of experiment, $p$ is success probability and $q$ is failure probability.

The probability of success, $p=\frac{3}{6}=\frac{1}{2}$

The probability of failure, $q=\frac{3}{6}=\frac{1}{2}$

Total number of trials, $n=5$

So, the variance, $npq=\frac{5}{4}$