In a class, the average age of boys is 14 years and that of girls is 12 years. The number of girls is 8 more than the number of boys. What is the average age of all students in the class?

To find the combined average, we need the number of boys and girls. Let boys = b, then girls = b + 8. Total students = 2b + 8. Weighted average = (14b + 12(b+8))/(2b+8) = (26b + 96)/(2b+8) = (13b + 48)/(b+4). This gives different results for different values of b. For b=8: average = (104+96)/16 = 12.5. For b=12: average = (156+96)/20 = 12.6. The answer varies with the number of boys, so data is inadequate.