Averages

Step 1: Understanding the problem.
We are given:
The number of boys is 30 and their average age is 12 years.
The number of girls is 60 and their average age is 10 years.
We need to find the average age of the entire class.
Step 2: Calculate the total age of the boys and girls.
The total age of the boys is:
{Total age of boys} = {Number of boys} × {Average age of boys} = 30 × 12 = 360 years
The total age of the girls is:
{Total age of girls} = {Number of girls} × {Average age of girls} = 60 × 10 = 600 years
Step 3: Calculate the total age of the whole class.
The total age of the whole class is the sum of the total age of boys and girls:
{Total age of the class} = 360 + 600 = 960 years
Step 4: Calculate the total number of students.
The total number of students is:
{Total number of students} = 30 + 60 = 90 students
Step 5: Calculate the average age of the class.
The average age of the whole class is given by:
{Average age of the class} = (Total age of the class) / (Total number of students) = 960 / 90 = 10.66 years
Step 6: Conclusion.
Thus, the average age of the whole class is 10.66 years.
Therefore, the correct answer is (2) 10.66 years.