Prem starts to school from his house and walks 400 metres towards north, turns left and walks 100 metres, turns left and walks 200 metres, turns left and walks 100 metres. How far he is away from his house?
The average age of eight teachers in a school is 40 years. A teacher among them died at the age of 55 years whereas another teacher whose age was 39 years joins them. The average age of the teachers in the school now is (in years)