The marks obtained (out of 50) by a batch of students are grouped as follows:
Class interval (marks): 5–15 15–25 25–35 35–45
Frequency: 4 6 x 5
If the mean mark of the distribution is 25, answer the following.
(a) Calculate the missing frequency x. Show all steps clearly.
(b) Using the value of x obtained in part (a), find the total number of students and verify that the mean is indeed 25.