Answer
112.5 ft
Work Step by Step
1. Similar triangle problems. Ratio. You need to put shadow over shadow and set it equal to actual height over actual height of the building.
$\frac{40}{300}=\frac{15}{b}$
2. Then solve for b:
$40b=4500$
$b=112.5$
3. Don't forget the units 112.5 ft
