Question 23

loading...

Prev/Next links

Jambmaths question: 

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

Option A: 

9

Option B: 

7

Option C: 

42

Option D: 

15

Jamb Maths Solution: 

$\begin{align}  & \text{Let the number of students}=x \\ & \text{Mean age of the students}={{{\bar{x}}}_{students}}=15 \\ & \text{Teacher age }=45 \\ & \text{Mean age of teacher and students}={{{\bar{x}}}_{teacher+students}} \\ & {{{\bar{x}}}_{teacher+students}}=18 \\ & \text{Total ages of the students }=15x \\ & \text{Total ages of the students and teacher }=15x+45 \\ & \text{Mean age of students and teacher}={{{\bar{x}}}_{teacher+students}} \\ & {{{\bar{x}}}_{teacher+students}}=18=\frac{15x+45}{x+1} \\ & 15x+45=18(x+1) \\ & 15x+45=18x+18 \\ & 3x=27 \\ & x=9 \\ & \text{The numbers of students are 9} \\\end{align}$

Jamb Maths Topic: 
Year of Exam: