Marks obtained by 7 students in a subject are 30, 55, 75, 90, 50, 60, 39. The number of students securing marks less than the mean marks is

Options

A. 7
B. 6
C. 5
D. 4

Explanation

To solve the problem, we need to find the mean of the marks obtained by the 7 students and then determine how many students scored less than this mean.

### Step-by-Step Solution:

1. **List the Marks**:
The marks obtained by the 7 students are:
\[ 30, 55, 75, 90, 50, 60, 39 \]

2. **Calculate the Total Marks**:
To find the mean, we first need to calculate the total marks obtained by all students.
\[ \text{Total Marks} = 30 + 55 + 75 + 90 + 50 + 60 + 39 \]

Performing the addition:
\[ = 30 + 55 = 85 \]
\[ = 85 + 75 = 160 \]
\[ = 160 + 90 = 250 \]
\[ = 250 + 50 = 300 \]
\[ = 300 + 60 = 360 \]
\[ = 360 + 39 = 399 \]

So, the total marks are \(399\).

3. **Calculate the Mean**:
The mean is calculated by dividing the total marks by the number of students.
\[ \text{Mean} = \frac{\text{Total Marks}}{\text{Number of Students}} = \frac{399}{7} \]

Performing the division:
\[ 399 \div 7 = 57 \]

Therefore, the mean marks are \(57\).

4. **Count Students Below the Mean**:
Now, we need to find out how many students scored less than the mean marks of \(57\). We will compare each student's marks with the mean:
- \(30 < 57\) (Yes)
- \(55 < 57\) (Yes)
- \(75 < 57\) (No)
- \(90 < 57\) (No)
- \(50 < 57\) (Yes)
- \(60 < 57\) (No)
- \(39 < 57\) (Yes)

The students who scored less than \(57\) are:
- 30
- 55
- 50
- 39

Thus, there are **4 students** who scored less than the mean marks.

### Final Answer:
The number of students securing marks less than the mean marks is **4**.

---