Engineering Board Exam Reviewer · Related Rates (Time Rates) · medium
Two cars start from the same intersection at the same time. One travels north at 60 kph, the other east at 80 kph. Find the rate at which the distance between them is increasing after 3 hours.
- 100 kph
- 140 kph
- 70 kph
- 120 kph
Answer
A. 100 kph
Solution
Since both travel at constant speed from the same point in perpendicular directions, the separation rate is constant: sqrt(602+802)=sqrt(3600+6400)=sqrt(10000)=100 kph.
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