Average weight of a group of 11 students is 37 kg. When a student left the group, then average weight of the group becomes 35 kg. What is the weight (in kg.) of the student who left?

Options

A. 65
B. 59
C. 57
D. 70

Answer

To find the weight of the student who left the group, we can follow these steps:

### Step 1: Calculate the total weight of the 11 students.
The average weight of the group of 11 students is given as 37 kg. We can use the formula for average:

\[ \text{Average} = \frac{\text{Total Weight}}{\text{Number of Students}} \]

Rearranging this formula to find the total weight gives us:

\[ \text{Total Weight} = \text{Average} \times \text{Number of Students} \]

Substituting the values:

\[ \text{Total Weight} = 37 \, \text{kg} \times 11 = 407 \, \text{kg} \]

### Step 2: Calculate the total weight after one student leaves.
After one student leaves, the average weight of the remaining 10 students becomes 35 kg. We can again use the average formula:

\[ \text{Total Weight of Remaining Students} = \text{Average} \times \text{Number of Remaining Students} \]

Substituting the values:

\[ \text{Total Weight of Remaining Students} = 35 \, \text{kg} \times 10 = 350 \, \text{kg} \]

### Step 3: Find the weight of the student who left.
To find the weight of the student who left, we need to subtract the total weight of the remaining students from the total weight of the original group:

\[ \text{Weight of Student Who Left} = \text{Total Weight} - \text{Total Weight of Remaining Students} \]

Substituting the values:

\[ \text{Weight of Student Who Left} = 407 \, \text{kg} - 350 \, \text{kg} = 57 \, \text{kg} \]

### Conclusion:
The weight of the student who left is **57 kg**.

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