Question

3) The average age of 30 students in a class
is 12 years. If another 6 students whose
average age is 15 years are also joined
in this class, now the average age of all
students is. ​

Answer 1

$average \: age = \frac{360 + 90}{30 + 6} = \frac{450}{36} \\ = 12 \ \frac{1}{2}$