The average weight of 5 students in a class is 25.8 kg. When a new student joined them, the average weight is increased by 3.9 kg. Find the approximate weight of the new student.

Options

A. 55 kg
B. 49 kg
C. 42 kg
D. 44 kg

Answer

To find the approximate weight of the new student who joined the class, we can follow these steps:

### Step 1: Calculate the total weight of the original 5 students.
The average weight of the 5 students is given as 25.8 kg.

To find the total weight of these 5 students, we use the formula:
\[ \text{Total Weight} = \text{Average Weight} \times \text{Number of Students} \]
Substituting the values:
\[ \text{Total Weight} = 25.8 \, \text{kg} \times 5 = 129 \, \text{kg} \]

### Step 2: Determine the new average weight after the new student joins.
When the new student joins, the average weight increases by 3.9 kg. Therefore, the new average weight is:
\[ \text{New Average Weight} = 25.8 \, \text{kg} + 3.9 \, \text{kg} = 29.7 \, \text{kg} \]

### Step 3: Calculate the total weight of the 6 students.
Now, we have 6 students in total. To find the total weight of these 6 students, we again use the average weight:
\[ \text{Total Weight of 6 Students} = \text{New Average Weight} \times \text{Number of Students} \]
Substituting the values:
\[ \text{Total Weight of 6 Students} = 29.7 \, \text{kg} \times 6 = 178.2 \, \text{kg} \]

### Step 4: Calculate the weight of the new student.
To find the weight of the new student, we subtract the total weight of the original 5 students from the total weight of the 6 students:
\[ \text{Weight of New Student} = \text{Total Weight of 6 Students} - \text{Total Weight of 5 Students} \]
Substituting the values:
\[ \text{Weight of New Student} = 178.2 \, \text{kg} - 129 \, \text{kg} = 49.2 \, \text{kg} \]

Thus, the approximate weight of the new student is **49.2 kg**.