In a class there are 25 students whose average age is decreased by 3 months when student aged 22 years is replaced by a new student. Find the age of the new student.

When a student aged 22 years is replaced and the average decreases by 3 months (0.25 years), the new student's age is 22 - (25 × 0.25) = 22 - 6.25 = 15.75 years, which is 15 years and 9 months. The closest option is 16 years 4 months, but it's not exact. The calculation: Average decrease = (Old age - New age) / 25, so New age = 22 - (0.25 × 25) = 15.75 years = 15 years 9 months.