The first group of students consists of 10 and their average age was 13 years old the next group consisted of 30 students and their average was 9 years old find the average age of both groups?
[10 students x their average age (13) + 30 students x their average age (9) ] / [10 students + 30 students =40]
=[130 + 270] / 40 =10 years - the average age of ALL students (Both groups)
