On a field trip when their bus breaks down 40 miles from the school. a teacher takes 5 of them back to school in her car, travelling at an average speed of 40 miles per hour.
the other 5 students start walking towards school at a steady 4 miles per hour.
the teacher drops the 5 at school. then immediately turns around and comes back for the others, again travelling at a steady speed of 40 miles per hour. how far have the students walked by the time the car reaches them?