Total age of students = Average age × Number of students Total age of the group = Average age × Number of people in the group Age of the teacher = Total age of the group - Total age of students Calculation: Total age of 48 students =22×48 ⇒ Total age of 48 students = 1056 Total age of 49 people (students + teacher) = 23×49 ⇒ Total age of 49 people =1127 Age of the teacher = Total age of 49 people - Total age of 48 students ⇒ Age of the teacher =1127−1056 ⇒ Age of the teacher =71