The average age of a class of 39 students is 15 years. If the age of the teacher be included, then the average increases by 3 months. Find the age of the teacher.
Total age of 39 persons = (39 x 15) years = 585 years.
Average age of 40 persons= 15 yrs 3 months = 61/4 years.
Total age of 40 persons = ((61/4 )x 40) years= 610 years.
∴ Age of the teacher = (610 - 585) years=25 years.
