3. Four boys, four girls, and a coach are arranged on a circular track. Each girl stands diametrically opposite one of the boys. The length of the track is 50m. On the coach's command, all of them run to him along the shortest path on the track. What is the total distance all the children will run together?
Answer: $100 \mathrm{m}$.

Solution. Consider a pair - a boy and a girl standing diametrically opposite each other - and the coach. It is clear that these boy and girl together will run half a circle, that is, 25 meters. Since there are four pairs, all the children together will run $4 \cdot 25=100$ m.
Criteria. Answer based on specific cases: 1 point.