There are 20 students with an average height of 125 cm in a class. 5 students with an average height of 116 cm leave the class. What is average height of the class now?

Options

A. 118 cm
B. 120 cm
C. 128 cm
D. 130 cm

Answer

To find the new average height of the class after 5 students leave, we can follow these steps:

### Step 1: Calculate the total height of the original 20 students.
The average height of the 20 students is 125 cm. Therefore, the total height can be calculated as:
\[ \text{Total Height} = \text{Average Height} \times \text{Number of Students} = 125 \, \text{cm} \times 20 = 2500 \, \text{cm} \]

### Step 2: Calculate the total height of the 5 students who leave.
The average height of the 5 students who leave is 116 cm. Therefore, the total height of these students is:
\[ \text{Total Height of Leaving Students} = \text{Average Height} \times \text{Number of Students} = 116 \, \text{cm} \times 5 = 580 \, \text{cm} \]

### Step 3: Calculate the total height of the remaining students.
Now, we need to subtract the total height of the leaving students from the total height of the original students:
\[ \text{Total Height of Remaining Students} = \text{Total Height} - \text{Total Height of Leaving Students} = 2500 \, \text{cm} - 580 \, \text{cm} = 1920 \, \text{cm} \]

### Step 4: Calculate the number of remaining students.
After 5 students leave, the number of remaining students is:
\[ \text{Remaining Students} = 20 - 5 = 15 \]

### Step 5: Calculate the new average height of the class.
Now, we can find the new average height by dividing the total height of the remaining students by the number of remaining students:
\[ \text{New Average Height} = \frac{\text{Total Height of Remaining Students}}{\text{Remaining Students}} = \frac{1920 \, \text{cm}}{15} = 128 \, \text{cm} \]

### Final Answer:
The average height of the class now is **128 cm**.

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