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December 22, 2014

December 22, 2014

Posted by **Trevor** on Thursday, February 28, 2013 at 12:01pm.

- Calculus -
**Steve**, Thursday, February 28, 2013 at 12:40pmIf the man is x away from the lamp, and his shadow is s,

s/6 = (x+s)/20

s = 3/7 x

so,

ds/dt = 3/7 * dx/dt = 3/7 (-5) = -15/7 ft/s

- Calculus -
**Trevor**, Thursday, February 28, 2013 at 1:52pmI dont know if this is right because if you are using x for the distance the man is away from the light post then you cant set x equal to the rate at which the man is walking.

- Calculus -
**Steve**, Thursday, February 28, 2013 at 3:21pmYou are correct. However, dx/dt

*is*the rate he is walking away. That is the value I used.

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