A street light is mounted at the top of a 15 foot-tall pole. A man 6 ft tall walks away from the pole with the speed of 5 ft/s along a straight path. How fast is the tip of his shadow moving when he is 40 ft from the pole?

Question

anonymous · Answer

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anonymous · Answer

similar triangles all over the place, so you have lots of choices to relate $x$ and$y$
you are told $y'=5$ and you want $x'$ when $y=40$

anonymous · Answer

you could for example use $\frac{x}{6}=\frac{x+y}{15}$

anonymous · Answer

So we dont know X, but we can find the triangle from  y, ( from the tip of the man) to the tip of the post. but youre left with an empty square?

anonymous · Answer

$x$ is the length of the shadow, and you are looking for $x'$ the rate of change of the shadow

anonymous · Answer

|dw:1353902217039:dw|   How are you suppose to solve for the missing part of z?