ANSWER
The length of the shadow is
[tex]412ft.[/tex]
EXPLANATION
The shadow cast by the building is
[tex]b \: ft[/tex]
long.
We use trigonometry to determine the length of b.
[tex]b[/tex]
is the length of the side that is adjacent to the 20° angle.
We also know the length of the side that is opposite to the 20° angle to be 150ft.
We now use the tangent ratio to determine the value of b.
[tex] \tan(20 \degree) = \frac{length \: of \: opposite \: side}{length \: of \:adjacent\: side} [/tex]
[tex]\Rightarrow \: \tan(20 \degree) = \frac{150ft} {b \: ft}[/tex]
[tex]\Rightarrow \: b = \frac{150} {\tan(20 \degree)}[/tex]
[tex]\Rightarrow \: b = 412.122ft[/tex]
To the neatest feet,the length of the shadow is
[tex]412ft.[/tex]