Question

the mean monthly salary of 12 teacher in a school is rupees 15000. Teacher retire from the school who get rupees 25000 per month what will be the mean monthly salary now
?

Answer 1

15000*12=180000
180000-25000=155000
mean=155000*11/11
=1705000/11
=155000

Answer 2

let x be the salary of all 12 teachers then according to question,
x/12= 15000.....(i)
and now when 1 teacher is retired then salary of 11 teachers is x-25000....(ii)
so, from (i) x=12*15000
                  x=180000
now put x=180000 in eq..(ii)
180000-25000=155000
so now new mean salary is
155000/11=14090.90