Question

A person is standing 40ft away from a street light that is 30ft tall. How tall is he if his shadow is 10ft long?

Answer 1

I got `6"ft"`

Explanation:

Considering the figure:

I would use trigonometry applied to the two triangles formed by the street light and the man writing:
Big one: `30/(40+10)=tan(alpha)`
Small one: `h/10=tan(alpha)`
substituting one into the other for `tan(alpha)` we get:
`30/50=h/10`
`h=30/50*10=6"ft"`
The two triangles are also similar so you can use the ratios of their sides and get the same result.