The mean age of a group of students is 15 years when the age of a teacher 45 years old is added to the ages of the students, the mean age becomes 18 years. Find the numbers of students in the group

Answer 1

Let's denote the number of students in the group as "n".

We know that the mean age of the group of students is 15 years, so the total age of the students is 15n.

When the age of the teacher (45 years) is added to the total age of the students, the mean age becomes 18 years. The new total age is 18(n + 1).

From this, we can set up the equation:
(15n + 45)/(n + 1) = 18

Solving this equation:
15n + 45 = 18(n + 1)
15n + 45 = 18n + 18
27 = 3n
n = 9

Therefore, there are 9 students in the group.