For two similar triangles, the ratios of the similar sides are constant, and the angles remain constant too.
Taking the ratio of the horizontal sides:
[tex]r=\frac{36ft}{10ft}=3.6[/tex]
Now, we use this ratio to calculate the height h of the building:
[tex]\begin{gathered} 3.6=\frac{h}{6} \\ \\ h=3.6\cdot6 \\ h=21.6ft \end{gathered}[/tex]
