Compare the motion of three speedboats. Which speedboat was moving at the lowest speed?

 - a speedboat that moved 1,030kilometers west in 10hours
 - a speedboat that moved 1,055kilometers south in 10hours
 - a speedboat that moved 955kilometers north in 10hours
Look at the distance each speedboat moved and the time it took to move that distance. The direction each speedboat moved does not affect its speed.
Notice that each speedboat moved for 10 hours. The speedboat that moved 955 kilometers moved the shortest distance in that time. So, that speedboat must have moved at the lowest speed.