Solution:-

Let us take \[10\] multiples of  \[3\] are  \[3,6,9,12,15,18,21,24,27,30\]

We know that Mean = \[\bar{X}=\sum\limits_{i=1}^{a}{{{x}_{i}}}\]

\[\overline{x}=(3+6+9+12+15+18+21+24+27+30)/10\]

= \[165/10\]

= \[16.5\]

Draw  the table of the data and append other columns after calculations.

Then, Variance

\[{{\sigma }^{2}}=\frac{1}{n}\sum\limits_{i=1}^{a}{{{({{x}_{i}}-\overline{x})}^{2}}}\]

=\[(1/10)\times 742.5\]

= \[74.25\]

Therefore, Mean = \[16.5\] and Variance = \[74.25\]