Find the mean and median for the following data :

Classes	Frequency
$\displaystyle 5$-$\displaystyle 15$	$\displaystyle 2$
$\displaystyle 15$-$\displaystyle 25$	$\displaystyle 3$
$\displaystyle 25$-$\displaystyle 35$	$\displaystyle 5$
$\displaystyle 35$-$\displaystyle 45$	$\displaystyle 7$
$\displaystyle 45$-$\displaystyle 55$	$\displaystyle 4$
$\displaystyle 55$-$\displaystyle 65$	$\displaystyle 2$
$\displaystyle 65$-$\displaystyle 75$	$\displaystyle 2$

\[\begin{array}{|c|c|c|c|c|} \hline \text { Classes } & \text { frequency }\left(f_{\mathrm{i}}\right) & x_{\mathrm{i}} & f_{\mathrm{i}} x_{\mathrm{i}} & c f \\ \hline 5-15 & 2 & 10 & 20 & 2 \\ 15-25 & 3 & 20 & 60 & 5 \\ 25-35 & 5 & 30 & 150 & 10 \\ 35-45 & 7 & 40 & 280 & 17 \\ 45-55 & 4 & 50 & 200 & 21 \\ 55-65 & 2 & 60 & 120 & 23 \\ 65-75 & 2 & 70 & 140 & 25 \\ \hline \text { Total } & 25 & & 970 & \\ \hline \end{array} \] Median class is $\displaystyle 35$-$\displaystyle 45$ \[\begin{aligned} \text { Median } & =35+\left(\frac{\dfrac{25}{2}-10}{7}\right) \times 10 \\ & =\frac{270}{7} \text { or } 38.57 \text { approx. } \end{aligned} \]