In a class, the average age of 40 students is 12 years when teacher’s age is included to it, the average increases by 1. The age of teacher is :
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 53 years
Average = sum of age / total number of students
Average (when excluding the age of teacher) = sum of age of 40 students / 40
12 = sum / 40
sum of age of 40 students = 40 × 12 = 480
Average (when including the age of teacher) = sum of age of 40 students + age of teacher / 41
480 + age of teacher = 41 × 13 = 533
age of teacher = 533 - 480 = 53 yrs