Question

The mean age of 20 students is 15 years.if the age of teacher is included then mean age is become 17 years. Find the age of teacher

Answer 1

Mean age of 20 students=15
their total  age will be =20x15=300
if teacher get add in them =20+1=21
their mean age=17
so                  17=300+x/21
                       17x21=300+x
                         357=300+x
                           x=357-300
                            x=57
     The present  age of the teacher is 57