Math Problem Statement

Two straight roads diverge at an angle of 60°. Two cars leave the intersection at 2:00 P.M., one traveling at 30 mi/h and the other at 32 mi/h. How far apart are the cars at 2:30 P.M.? (Round your answer to two decimal places.)

Solution

To solve the problem, we can visualize the cars’ paths as two sides of a triangle, where the angle between the two roads is 60°. The two cars travel at different speeds, forming the two sides of the triangle.

Steps:

  1. Time Duration:

    • The cars leave at 2:00 PM and the question asks for the distance at 2:30 PM, so the time difference is 30 minutes or 0.5 hours.
  2. Distances Traveled:

    • The first car travels at 30 mi/h for 0.5 hours. Distance = speed × time = 30×0.5=1530 \times 0.5 = 15 miles.
    • The second car travels at 32 mi/h for 0.5 hours. Distance = speed × time = 32×0.5=1632 \times 0.5 = 16 miles.
  3. Use of the Law of Cosines: Since the angle between the roads is 60°, and we have the two distances (15 miles and 16 miles), we can use the law of cosines to find the distance between the two cars: d2=a2+b22abcos(θ)d^2 = a^2 + b^2 - 2ab \cdot \cos(\theta) where:

    • a=15a = 15 miles,
    • b=16b = 16 miles,
    • θ=60\theta = 60^\circ,
    • and dd is the distance between the two cars.

    Substituting the values: d2=152+1622×15×16×cos(60)d^2 = 15^2 + 16^2 - 2 \times 15 \times 16 \times \cos(60^\circ) Since cos(60)=0.5\cos(60^\circ) = 0.5: d2=225+2562×15×16×0.5d^2 = 225 + 256 - 2 \times 15 \times 16 \times 0.5 d2=225+256240d^2 = 225 + 256 - 240 d2=241d^2 = 241 d=24115.52d = \sqrt{241} \approx 15.52

Therefore, the distance between the two cars at 2:30 PM is approximately 15.52 miles.

Would you like a more detailed explanation or have any questions?

Here are 5 related questions:

  1. How would the problem change if the cars traveled for 1 hour instead of 30 minutes?
  2. What would happen if the angle between the roads was 90° instead of 60°?
  3. How does the Law of Cosines apply to triangles with angles other than 60°?
  4. How can you use the Pythagorean theorem in this scenario if the angle was 90°?
  5. How would the situation differ if one car accelerated while traveling?

Tip: When solving problems involving angles and distances, always try to visualize the scenario and use trigonometric laws such as the Law of Cosines or Law of Sines when needed.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Distance Calculation
Law of Cosines

Formulas

d^2 = a^2 + b^2 - 2ab * cos(θ)
Distance = Speed × Time

Theorems

Law of Cosines

Suitable Grade Level

Grades 10-12