Question

A street light is mounted at the top of a 15-ft-tall pole. A man 6 ft tall walks away from the pole with a speed of 7 ft/s along a straight path. How fast is the tip of his shadow moving when he is 30 ft from the pole?

Answer 1

looks like you want to set up a relationship associated with right tirangles, or similar triangles

Answer 2

l/m = s/(d+s)

l(d+s) = ms

l'(d+s) + l(d+s)' = m's + ms'

since l and m are not changeing, l' and m'=0

l(d+s)' = ms' solve for s' to determine d'+s'

Answer 3

thank you i had already figured it out. the answer was 35/3 ft/s