Question

the average age of 30 boys of clads is 14 years,when the age of class teacher is included the average becomes 15years.find the age of class teacher

Answer 1

average=sumof something /no of something

let the sum be ages be X
=X/no of students
=X/30 is the average which is equal to 14
=X/30=14
=X=420 years
Now,
to this a teacher age is added ,
let the teacher age be Y

thus we can say their sum of ages will be the sum of ages of student and the teacher

=420+Y=sum

No of people will be 1 more than before as a teacher is included

=30+1=31=no of people

Average=420+Y/31 which is equal to 15

=420+Y/31=15
=420+Y=15×31
=420+Y=465
=Y=465-420
=Y=45
thus the age of the teacher is 45 years