5. Three athletes ran a distance of 3 kilometers. The first kilometer they ran at constant speeds $v_{1}, v_{2},$ and $v_{3}$ respectively, such that $v_{1}>v_{2}>v_{3}$. After the 1-kilometer mark, each of them changed their speed: the first from $v_{1}$ to $v_{2}$, the second from $v_{2}$ to $v_{3}$, and the third from $v_{3}$ to $v_{1}$. Who among the athletes finished last? (N. Chernega)
Answer. Second. Solution. The first athlete ran the distance faster than the second, as his speed was higher than the second's both on the first kilometer of the distance and on the last two. The third athlete spent as much time on the first kilometer as the second did on the second kilometer, and ran the second and third kilometers faster than the second ran the first and third kilometers. Therefore, he also finished before the second, which leads to the answer.