Let the total number of students be ‘x’ ∴ Sum of the ages of all students = 14x 0.25x number of students have an average age of 12 ∴ Sum of the ages of 25% students = 3x 0.4x number of students have an average age of 14 ∴ Sum of the ages of 40% students = 5.6x Sum of ages of (25% + 40% + rest of the students) = 14x ∴ 3x + 5.6x + Sum of the ages of the remaining 35% students = 14x ∴ Sum = 5.4x ∴ Their average age = 5.4x/(0.35x) = 15.4 ∴ The average age of the remaining students is 15.4 years