Compare the motion of three ships. Which ship was moving at the lowest speed?

 - a ship that moved 175kilometers south in 5hours
 - a ship that moved 215kilometers west in 5hours
 - a ship that moved 355kilometers north in 5hours
Look at the distance each ship moved and the time it took to move that distance. The direction each ship moved does not affect its speed.
Notice that each ship moved for 5 hours. The ship that moved 175 kilometers moved the shortest distance in that time. So, that ship must have moved at the lowest speed.