Question

A group of 20 students attempting a mathematical challenge have an average age of 11.When their teacher is included their average age is 12. What is the age of the teacher

Answer 1

Answer:

Teacher's age is 32.

Step-by-step explanation:

How you count the average age for people is:
(age of person 1 + age of person 2 ... ) / number of people = average age

Let's start by observing that we've got 2 equations coming from the text:

• average of just students
  20 students x 11 (average for a student) = sum of age of students
  20 x 11 = 220
• average of student and teacher
  let's say x is age of teacher
  together students & teacher is 20 + 1 = 21 people
  (20 students x 11 + x)/ (20 + 1) = 12
  (220 + x) / 21 = 12
  220 + x = 12 * 21
  x = 12 *21 - 220
  x = 252 - 220
  x = 32

hope this helps ❣️