An iron railway track is installed in winter at an average...

The gap to be provided between two adjacent sections must be equal to the expansion of one section to prevent compression.

The initial length of the track section is $L = 12.0\text{ m}$.

The change in temperature is \Delta T = 48^{}^{{}^{\circ}}\text{C} - 18^{}^{{}^{\circ}}\text{C} = 30^{}^{{}^{\circ}}\text{C}.

The coefficient of linear expansion is \alpha = 11 \times 10^{-6}^{}^{{}^{\circ}}\textC^{-1}.

The increase in length of one section is given by:

$\Delta L = L \alpha \Delta T$

Substituting the given values:

$\Delta L = 12.0 \times 11 \times 10^{-6} \times 30$

$\Delta L = 3960 \times 10^{-6}\text{ m}$

$\Delta L = 3.96 \times 10^{-3}\text{ m}$

Converting to centimeters:

$\Delta L = 0.396\text{ cm}$

Thus, a gap of $0.396\text{ cm}$ must be provided.