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

1 Answer
Gió
May 20, 2016

I got #6"ft"#

Explanation:

Considering the figure:
enter image source here
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.

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