7. (6 points) Ding Xiaole practiced jogging for 4 days last week. The farthest he ran in a day was 3.3 kilometers, and the shortest was 2.4 kilometers. Therefore, it can be calculated that over these 4 days, Ding Xiaole ran at most $\qquad$ kilometers, and at least $\qquad$ kilometers.
【Answer】Solution: Ding Xiaole ran the most:
$$
\begin{array}{l}
3.3 \times 3+2.4 \\
=9.9+2.4 \\
=12.3 \text { (km) }
\end{array}
$$

Ding Xiaole ran the least:
$$
\begin{array}{l}
2.4 \times 3+3.3 \\
=7.2+3.3 \\
=10.5 \text { (km) }
\end{array}
$$

Answer: Ding Xiaole ran the most 12.3 km, and the least 10.5 km. Therefore, the answers are: $12.3, 10.5$.