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**Tascja** A floodlight that is 15 m away and at ground level illuminates a building. A man 2 m tall walks away from the light directly towards the building at 2 m/s. Find the rate of change of the length of his shadow when he is 4 m from the light.

so far i have the the ratio is that the shadow is 15/2 when he is 4 m away. but when i plug in to get the rate of change im way off...

With the similar triangle do i have to compare the shadow to the length they give me or to his height???