Three groups of boys have average ages 20, 22, and 24 respectively. If the number of students in the three groups is in the ratio 1 : 3 : 6, what is the overall average age?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 23.
Let the number of boys in each group be x, 3x and 6x respectively.
Total age of first group = x × 20 = 20x
Total age of second group = 3x × 22 = 66x
Total age of third group = 6x × 24 = 144x
Total age of all groups = 20x + 66x + 144x = 230x
Overall average = 230x/10x = 23