An aluminium and steel rods having same lengths and cross-sections are joined to make total length of \( 120 \, \text{cm} \) at \( 30^\circ\text{C} \). The coefficient of linear expansion of aluminium and steel are \( 24 \times 10^{-6} \, / \, ^\circ\text{C} \) and \( 1.2 \times 10^{-5} \, / \, ^\circ\text{C} \), respectively. The length of this composite rod when its temperature is raised to \( 100^\circ\text{C} \), is ________ \( \text{cm} \).
