The ratio between the lengths of the posts must be equivalent to the ration between the lengths of their shadows. Then, if x is the length of the shadow of the longer post, we have:
[tex]\begin{gathered} \frac{x}{0.85}=\frac{2}{0.45} \\ x=\frac{2\cdot0.85}{0.45} \\ x\approx3.78\text{ m} \end{gathered}[/tex]
