An oval running track has two straight sides joined by two semicircular ends. Two runners start together and each runs one full lap, one along the inner edge of a lane and the other along the inner edge of the next lane out, the two paths being 1.4 m apart all the way round. How many metres further does the outer runner cover? Take π = 22/7.

The two straights are the same length for both runners, so the whole difference comes from the bends. The two semicircular ends together make one complete circle, and the outer circle's radius is 1.4 m bigger, so the extra distance = 2π(1.4) = 2 × (22/7) × 1.4 = 8.8 m. The lengths of the straights never enter the answer, which is why staggered starts on a real track depend only on the lane width. (4.4 m counts one semicircular end only; 1.4 m is the lane width itself; 17.6 m doubles the radius gap to 2.8 m.)