Engineering Board Exam Reviewer · Related Rates (Time Rates) · medium
A 13-ft ladder rests against a vertical wall. If the top slides down the wall at 2 ft/s, find the rate at which the bottom is moving away from the wall when the top is 5 ft above the ground.
- 5/6 ft/s 0.833 ft/s
- 2 ft/s
- 1.2 ft/s
- 0.417 ft/s
Answer
A. 5/6 ft/s 0.833 ft/s
Solution
x2+y2=169. At y=5, x=12. Differentiating with dy/dt=-2: dx/dt=-y/xdy/dt=-5(-2)/12=5/6 0.833 ft/s.
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