#### 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