Compute the median from the following table
 

 

$\begin{array}{l}N=\mathrm{\Sigma }f=159\text{ (Odd number) }\\ \text{ Median is }\frac{1}{2}(n+1)=\frac{1}{2}(159+1)=80\text{ th value, which lies in }\end{array}$

$\text{ the class }30-40\text{ (see the row of cumulative frequency }95\text{ , which contains }80\text{ ). }$

$\text{ Hence median class is }30-40\text{ . }$

.'. We have 

l = Lower limit of median class = 30

 f = Frequency of median class = 45 

C = Total of all frequencies preceding median class = 50

 i  = Width of class interval of median class = 10 

$\begin{array}{r}\therefore \text{ Required median }=l+\frac{\frac{N}{2}-C}{f}\times i=30+\frac{\frac{159}{2}-50}{45}\times 10\\ =30+\frac{295}{45}=36.55\end{array}$