HELP: Question related to Mean, Mode, Median.................

How can I solve this? I dont see any number occurs the most for mode ? How can i find the answer for median?

The number of marks obtained by a group of 30 students for Mathematics test was as follows:

Marks ============>> 55,66,65,70,75,80,85
Frequency =========>> 5,4,7,7,3,2,1

Determine the Mode, Median and Mean.

Thanks in advance.

Note that 65 and 70 both have frequency 7. So there are two mode(viz. 65 &70). It is called bimodal.
Note that total frequency=29. So 15th term will be median. After arranging we can see 15th term is 66.
So, median is 66.
Mean=(55*5+66*4+65*7+70*7+75*3+80*2+85…
=67.38

Frequency means the number of times it has occured. So the marks 65 and 70 have occured the most number of times(7 times). Thus they are both modes

To calculate mean: sum (marks*frequency) / sum(frequency) => (55*5 + 60*4 + 65*7 +...) / (5 + 4 + 7+..,)

To calculate median: Write out each mark in increasing order the number of times it occurs, and the central mark is median: 55 55 55 55 55 60 60 60 60 65 65 65 65 65 65 65 70 70 .... and so on. There are 29 numbers, so the 15th one on the list is the median

55x5+66x4+65x7+70x7+75x3+80x2+85x1/29 the mean
The median is the middle value, rewrite it 55,65,66,70,75,80.85 so 70
The mode is the number that is repeated more often than any otherso 65 and 70

Mode= 66
Mean= 67
Median= 70