Compare the motion of two bowhead whales. Which bowhead whale was moving at a lower speed?

 - a bowhead whale that moved 15kilometers in 5hours
 - a bowhead whale that moved 10kilometers in 5hours
Look at the distance each bowhead whale moved and the time it took to move that distance.
One bowhead whale moved 10 kilometers in 5 hours.
The other bowhead whale moved 15 kilometers in 5 hours.
Notice that each bowhead whale spent the same amount of time moving. The bowhead whale that moved 10 kilometers moved a shorter distance in that time. So, that bowhead whale must have moved at a lower speed.