Question

A person who is 6ft tall walks away from a streetlight. When the person is 15 feet away from the light, the tip of his shadow is 5 feet in front of him. Find the height of the streetlight

Answer 1

We essentially have a ratio here:
$\frac{shadow}{actual}$

Since we know the ratio is going to stay constant at $\frac{5}{6}$, we can use this to find the height of the lamp along with the information that the total distance from the lamp to the tip of his shadow is 20:
$\frac{5}{6}=\frac{20}{h}$
$5h=120$
$h=24$