Originally Posted by
NeoSonata A spotlight on the ground shines on a wall 12 m away. If a man 2 m tall walks from the spotlight toward the building at a speed of 2.5 m/s, how fast is the length of his shadow on the building decreasing when he is 4 m from the building? (Round your answer to two decimal places.)
using similar triangles:
y/12 = 2/12-x
y = 12 / 12-x
y = 24 (12-x)^-1
dy/dt = -24(12-x)^-2 (-dx/dt)
dy/dt = 24(dx/dt) / (12-x)^2
Given:
dy/dt = ?
dx/dt = -2.5
x = 4
Plug in:
dy/dt = 24(-2.5) / (12-4)^2
dy/dt = -.9375
dy/dt = -.94
Web assigned marked my final answer wrong.
Why is my answer wrong?
Thanks.