When he is 4 m from the building, he is 8 m from the spotlight. The length of his shadow on the building at that time is 3 m.
The length of his shadow on the building when he is x meters from the spotlight is
Y = 2*(12/x) = 24/x
dY/dt = (dY/dx)*(dx/dt) = -(24/x^2)*1.6
= -(24/64)*1.6 = -0.6 m/s
If any body can solve this I would be greatly appreciative. I spent an hour in the tutoring center and no one could solve. Here goes:
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