Compare the motion of three ducks. Which duck was moving at the lowest speed?

 - a duck that moved 310kilometers north in 5hours
 - a duck that moved 365kilometers south in 5hours
 - a duck that moved 425kilometers west in 5hours
Look at the distance each duck moved and the time it took to move that distance. The direction each duck moved does not affect its speed.
Notice that each duck moved for 5 hours. The duck that moved 310 kilometers moved the shortest distance in that time. So, that duck must have moved at the lowest speed.