Measuring Space: Perimeter and Area

What “Measuring Space: Perimeter and Area” begins with

The tracks are laid out, and the athletes are all set to go racing down the tracks. Do you notice that the athletes are not at the same starting line? Those in the outer lanes seem to be starting ahead of those in the inner lanes while the finish line is the same for all of them. The distance between the starting points of adjacent lanes is called the ‘stagger’.