Related Rates Calculus
posted by Sisi .
A man 1.8 m tall is walking at a rate of 1.5 m/s away from a streetlight. It is found that the length of his shadow is increasing at a rate of 0.9 m/s. How high above the ground is the streetlight?

Related Rates Calculus 
Steve
If the man's distance is x, and the shadow's length is s, and the light is at height h, then using similar triangles,
1.8/s = h/(x+s)
or,
1.8x + 1.8s = hs
1.8x = s(h1.8)
1.9 dx/dt = (h1.8) ds/dt
Now plug in your numbers and solve for h. 
Related Rates Calculus 
Sisi
Thank you so so much!:)
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