GIVEN: Average age of 15 students of group = 24 years FORMULA USED: Average =
Sum of numbers
Total numbers
CALCULATION: Sum of ages of 15 students = 15 × 24 = 360 years Sum of ages of 12 students when 3 students left the group = 360 – 8 – 11 – 29 = 312 years New average age of the group = 312/12 = 26 years