13. Xiao Qiang did an experiment while drinking a cup of beverage. He inserted a chopstick vertically into the bottom of the cup and measured the part that was wet, which was exactly 8 centimeters; then he turned the chopstick around and inserted the other end straight into the bottom of the cup, and found that the dry part of the chopstick was exactly half the length of the wet part. How long is the chopstick in centimeters?
【Solution】Solution: $8 \times 2 \times \frac{1}{2}+8 \times 2$
$$
\begin{array}{l}
=8+16, \\
=24 \text { (cm). }
\end{array}
$$

Answer: The chopstick is 24 cm long.