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A 5 m ladder's foot slides from the wall at 3 m/s. How fast does the top fall when the foot is 3 m away?
A3/4 m/s
B16/9 m/s
C9/4 m/s
D4/3 m/s
Answer & Solution
Correct answer: C. 9/4 m/s
With x² + y² = 25, y = 4 and dx/dt = 3: dy/dt = −x(dx/dt)/y = −9/4, so the top falls at 9/4 m/s.
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