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Homework Help: Related Rates

  1. Nov 15, 2007 #1
    1. The problem statement, all variables and given/known data
    A man 6 ft tall wlaks at a rate of 5ft/s away from a light that is 15ft above the ground. when he is 10 ft from the base of the light,

    1) at what rate is the tip of his shadow moving?
    2) at what rate is the length of his shadow changing?

    The answers are
    1) -50/7 ft/s
    2)-15/7 ft/s

    3. The attempt at a solution
    I think that similar triangles come into play, and I belive that I need to establish two varibles and use implicit differentation. Any help would be greatly appreciated.

  2. jcsd
  3. Nov 15, 2007 #2
    yes, similar triangles comes into play. the length from the pole to the man is x, while the length from the pole to the man's show is x+y.
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