There are 30 boys and 60 girls in a class . If the average age of boys is 12yr and average age of girls is 10yr , then find out the average age of the whole class .

Answer

To find the average age of the whole class, we can follow these steps:

### Step 1: Find the total age of boys
To calculate the total age of boys, we use the formula:
\[ \text{Total Age of Boys} = \text{Number of Boys} \times \text{Average Age of Boys} \]
Given:
- Number of Boys = 30
- Average Age of Boys = 12 years

Calculating:
\[ \text{Total Age of Boys} = 30 \times 12 = 360 \text{ years} \]

### Step 2: Find the total age of girls
Next, we calculate the total age of girls using the same formula:
\[ \text{Total Age of Girls} = \text{Number of Girls} \times \text{Average Age of Girls} \]
Given:
- Number of Girls = 60
- Average Age of Girls = 10 years

Calculating:
\[ \text{Total Age of Girls} = 60 \times 10 = 600 \text{ years} \]

### Step 3: Find the total age of the whole class
Now, we can find the total age of the whole class by adding the total ages of boys and girls:
\[ \text{Total Age of Class} = \text{Total Age of Boys} + \text{Total Age of Girls} \]
Calculating:
\[ \text{Total Age of Class} = 360 + 600 = 960 \text{ years} \]

### Step 4: Find the total number of students
To find the total number of students in the class, we add the number of boys and girls:
\[ \text{Total Number of Students} = \text{Number of Boys} + \text{Number of Girls} \]
Calculating:
\[ \text{Total Number of Students} = 30 + 60 = 90 \]

### Step 5: Calculate the average age of the whole class
Finally, we find the average age of the whole class using the formula:
\[ \text{Average Age of Class} = \frac{\text{Total Age of Class}}{\text{Total Number of Students}} \]
Calculating:
\[ \text{Average Age of Class} = \frac{960}{90} \approx 10.67 \text{ years} \]

### Final Answer
The average age of the whole class is approximately **10.67 years**.

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