Can you post some videos on related to Mean , Median and Mode for grouped data?

Hi Sal , 

Can you post some videos on related to Mean , Median and Mode for grouped data.

I have a small question related to the above median for grouped data.

Interval     Frequency   Cumulative frequency

0 - 10              20                   20     

10 - 20             1                    21 

20 - 30             2                    23

30 - 40             3                    26 

40 - 50             4                    30

then the median for the above grouped data ? 

Please reply me.

Thank you,

Venkata Kishore