Find the median of the following data

Explanation

We prepares the cumulative frequency table , as given below

Now `N=90 rArr N/2=45`
The cumulative freqeuency just greater than 45 is 65 and the corresponding class is 50-60
Thus the median class is 50-60
then Midian Model of Grouped Data , Cumulative Frequency Graph and Ogive 841
`therefore I=50, h=10, f=20, cf=c.f. " of preceding class " =45, and N/2=45`
Median, `M_e=l+{hxx((N/2-cf))/f}=50+{10xx((45-45))/(20)}=50+0=50`
Hence the median mark is 50