Find the mode of the following marks (out of 10) obtained by 20 students.

4, 6, 5,9, 3,2, 7, 7, 6, 5,4, 9, 10, 10,3, 4, 7, 6, 9, 9

On arranging the given data in ascending order, we get

2, 3,3,4,4,4, 5,5,6,6,6, 7, 7, 7,9,9,9,9,10,10

Here, 9 occurs most frequently, i.e. four times. So, the required mode is 9.