The average age of a teacher and three students is 20 years. If all the three students are of same age and the difference between the age of the teacher and each student is 20 years, then what is the age of the teacher?

Traditional Method Let the age of Teachers is T years and the three students is a years (Given age of all three student is same). According to question,

(T + 3a)/4 = 20 or T + 3a = 80 ….(1)

T – a = 20 ….(2) (assuming that teachers age will be greater than the students)

By solving equations 1 and 2 simultaneously we have a = 15 and T = 35. Option (c) is correct.