While note down of marks scored in an examination by the students of a class, by mistake the marks scored by one student got recorded as 86 in place of 68 and thereby the average marks increase by 0.6 . What was the number of students in the class?

15 25 50 30

30

Difference in marks due to mistake  = 86 - 68 = 18 According to question ,    .6 unit = 18  1 unit = 30  So, Total number of students  = 30