The average age of 14 girls and their teacher’s age is 15 years. If the teacher’s age is excluded, the average reduces by 1. What is the teacher’s age?

the average age of 14 girls and teacher is given as 15 and as we know

Average = $$\frac {sum of ages}{number ofpersons}$$

Sum of ages of girls and teachers = 15×15 =225 years

Now the age of teacher is excluded and as a result the average reduced by 1 .So

New average = 14

New number of persons = 14

Hence new sum of ages after exclusion of teacher = 14x 14 = 196

Hence age of teacher =225-196 = 29 years