Compare the motion of two sailboats. Which sailboat was moving at a higher speed?

 - a sailboat that moved 170kilometers in 10hours
 - a sailboat that moved 100kilometers in 10hours
Look at the distance each sailboat moved and the time it took to move that distance.
One sailboat moved 170 kilometers in 10 hours.
The other sailboat moved 100 kilometers in 10 hours.
Notice that each sailboat spent the same amount of time moving. The sailboat that moved 170 kilometers moved a farther distance in that time. So, that sailboat must have moved at a higher speed.