Here's the question you clicked on:
rarnold14
A man 6 feet tall walks at a rate of 13 feet per second away from a light that is 15 feet above the ground. When he is 8 feet from the base of the light, at what rate is the tip of his shadow moving?
HINT HINT: Use similar Triangles!
another hint. the rate of change will be a constant, the "when he is 8 feet" will have nothing to do with it.
|dw:1320959290284:dw| use \[\frac{x}{6}=\frac{x+y}{15}\] to get a relation between x and y. you know \[y'=13\] and you want \[x'\]