Questions: Two cars start moving from the same point. One travels south at 20 mi / h and the other travels west at 15 mi / h. At what rate (in mi/h) is the distance between the cars increasing three hours later?

Two cars start moving from the same point. One travels south at 20 mi / h and the other travels west at 15 mi / h. At what rate (in mi/h) is the distance between the cars increasing three hours later?
Transcript text: Two cars start moving from the same point. One travels south at $20 \mathrm{mi} / \mathrm{h}$ and the other travels west at $15 \mathrm{mi} / \mathrm{h}$. At what rate (in mi/h) is the distance between the cars increasing three hours later?
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Solution

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Solution Steps

Step 1: Identify the speeds and directions of the cars
  • Car 1 travels south at 20 mi/h.
  • Car 2 travels west at 15 mi/h.
Step 2: Calculate the distances traveled by each car after 3 hours
  • Distance traveled by Car 1: \( 20 \text{ mi/h} \times 3 \text{ h} = 60 \text{ mi} \)
  • Distance traveled by Car 2: \( 15 \text{ mi/h} \times 3 \text{ h} = 45 \text{ mi} \)
Step 3: Use the Pythagorean theorem to find the distance between the cars
  • The cars form a right triangle with the distances traveled as the legs.
  • Let \( z \) be the distance between the cars.
  • \( z^2 = 60^2 + 45^2 \)
  • \( z^2 = 3600 + 2025 \)
  • \( z^2 = 5625 \)
  • \( z = \sqrt{5625} \)
  • \( z = 75 \text{ mi} \)

Final Answer

The distance between the cars is increasing at a rate of 25 mi/h.

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