## 2. Math Puzzle $7 / 65$

A $a=100 \mathrm{~m}$ long holiday train is rolling at a speed of $v_{Z}=72 \frac{\mathrm{km}}{\mathrm{h}}$.

How great is the speed $v_{W}$ of the wind hitting the train perpendicularly, if the smoke trail of the locomotive is deflected by the distance $b=40 \mathrm{~m}$ at the end of the train?
The locomotive has traveled $100 \mathrm{~m}$, while the smoke trail has traveled $40 \mathrm{~m}$. The wind speed $v_{W}$ must be in the same ratio to the train speed $v_{Z}$ as the distances traveled are to each other.

$$
\frac{100}{40}=\frac{72}{x} \rightarrow x=\frac{40 \cdot 72}{100}=28.8
$$

The wind speed $v_{W}$ is $28.8 \frac{\mathrm{km}}{\mathrm{h}}$.