We are laying 15 m long railway tracks at a temperature of $t=-8^{\circ} \mathrm{C}$. What gap must be left between the individual tracks if the maximum temperature we are planning for is $t=60^{\circ} \mathrm{C}$. The thermal expansion coefficient of the track is $\lambda=0,000012$.
If $x$ is the sought quantity, then

$$
\begin{gathered}
x=15\{1+\lambda(T-t)\}-15 \\
x=15 \lambda(T-t)=12.24 \text{ mm}
\end{gathered}
$$

(Jeno Guman, Losonc.)