Engineering Board Exam Reviewer · Related Rates (Time Rates) · medium
An airplane flies at a constant height of 4 miles above an observer, moving horizontally at 300 mph. Find the rate at which the distance from the plane to the observer is changing when the horizontal distance is 3 miles.
- 180 mph
- 240 mph
- 300 mph
- 150 mph
Answer
A. 180 mph
Solution
D2=x2+16. At x=3, D=5. Differentiating: dD/dt=x/Ddx/dt=3/5(300)=180 mph.
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