The average velocity of the entire trip is given by Eq. 4-8, vavg  r / t,
where the total displacement r  r  r  r 123
is the sum of three displacements (each result of a constant velocity during a given time), and t  t1  t2  t3 is the total
amount of time for the trip. We use a coordinate system with +x for East and +y for North.​