Find the median of the given data.

$\begin{array}{cccccc}\text{Wages (in Rs.)}& 200-300& 300-400& 400-500& 500-600& 600-700\\ \text{No. of Labourers}& 3& 5& 20& 10& 6\end{array}$

The correct option is C. 470

Less than frequency distribution for the data is :

$\begin{array}{ccc}\text{Wages}& \text{Frequency}& \text{Cumulative frequency}\\ 200-300& 3& 3\\ 300-400& 5& 8\\ 400-500& 20& 28\\ 500-600& 10& 38\\ 600-700& 6& 44\end{array}$

In the above distribution the total number of observations (labourers) is 44. Hence n = 44.
$\frac{n}{2}=22$.
The cumulative frequency that is greater than 22 but closest to 22 is 28. The class corresponding to this frequency is 400-500. This is the median class.
$\text{Median}=l+\left(\frac{\frac{n}{2}-cf}{f}\right)\times h$
Where,
$l$ = lower limit of median class,
$n$ = number of observations,
$cf$ = cumulative frequency of class preceding the median class,
$f$ = frequency of median class,
$h$ = class size (assuming class size to be equal)
For the given class,
$l=400$
$n=44$
$cf=8$
$f=20$
$h=100$
$\text{Median}=400+\left[\frac{22-8}{20}\right]\times 100$
$=400+(22–8)\times 5$
$=400+70$
$=470$
$\therefore$ The median is 470.