A plane that carries mail makes a round trip each day from Chicago to New York. It makes 3 intermediate stops on the way to New York and 1 intermediate stop on the way back to Chicago. Suppose you make a graph of the altitude of the plane for one day, with time on the horizontal axis and altitude on the vertical axis. How many times will the graph touch the horizontal axis?
A) 7
B) 6
C) 4
D) 11

Question

A plane that carries mail makes a round trip each day from Chicago to New York. It makes 3 intermediate stops on the way to New York and 1 intermediate stop on the way back to Chicago. Suppose you make a graph of the altitude of the plane for one day, with time on the horizontal axis and altitude on the vertical axis. How many times will the graph touch the horizontal axis?
A) 7
B) 6
C) 4
D) 11

anonymous · Answer

A.
Counting the takeoff, there are 3 touchdowns for the 3 intermediate stops and one for NY.
On the return flight there is 1 touchdown at an intermediate stop and one for Chicago making 7 contacts with the horizontal axis overall.