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

 - a duck that moved 375kilometers north in 5hours
 - a duck that moved 495kilometers west in 5hours
 - a duck that moved 315kilometers north 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 495 kilometers moved the farthest distance in that time. So, that duck must have moved at the highest speed.