1. Step 1: Calculate the sum of all the marks.
- X: 5
- 5: 15
- 25: 35
- 45: 55
- 65: 70
- F: 5
- 12: 27
- 15: 42
- 25: 67
- 8: 75
- 3: 78
- 2: 80

Sum of all marks = 80

2. Step 2: Calculate the total number of students.
- There are 12 students.

3. Step 3: Calculate the average marks.
- Average marks = Sum of all marks / Total number of students
- Average marks = 80 / 12
- Average marks = 6.67

Therefore, the average marks of the given students using the direct method is 6.67.



1. Step 1: Calculate the midpoint of each class interval.
- X: 2.5
- 5: 7.5
- 15: 17.5
- 25: 27.5
- 35: 37.5
- 45: 47.5
- 55: 57.5
- 65: 67.5
- F: 72.5
- 5: 7.5
- 12: 17.5
- 15: 17.5
- 25: 27.5
- 8: 12.5
- 3: 7.5
- 2: 2.5

2. Step 2: Calculate the deviation of each midpoint from the assumed mean.
- Assumed mean = 40
- Deviation for each midpoint = Midpoint - Assumed mean

3. Step 3: Calculate the product of frequency and deviation for each midpoint.
- X: 0 * 2.5 = 0
- 5: 1 * 7.5 = 7.5
- 15: 1 * 17.5 = 17.5
- 25: 1 * 27.5 = 27.5
- 35: 1 * 37.5 = 37.5
- 45: 1 * 47.5 = 47.5
- 55: 1 * 57.5 = 57.5
- 65: 1 * 67.5 = 67.5
- F: 1 * 72.5 = 72.5
- 5: 1 * 7.5 = 7.5
- 12: 1 * 17.5 = 17.5
- 15: 1 * 17.5 =