Math Problem Statement

Car A is traveling at a speed of 54 km/h on a road. Car B is 100 meters behind Car A, traveling in the same direction as Car A. Car C is traveling along the same road towards Car A in the opposite direction at a speed of 72 km/h and is 280 meters away from Car A. At what speed (in km/h) should Car B travel so that all three cars meet at the same time?

  1. 95.4
  2. 99 3)101 4)106.2

Solution

We are given the following details:

  • Car A is traveling at 54 km/h.
  • Car B is 100 meters behind Car A, traveling in the same direction as Car A.
  • Car C is 280 meters ahead of Car A, traveling towards Car A at 72 km/h.

We need to find the speed of Car B such that all three cars meet at the same time.

Step-by-step solution:

  1. Convert distances to kilometers:

    • Car B is 100 meters behind Car A: 100m=0.1km100 \, \text{m} = 0.1 \, \text{km}
    • Car C is 280 meters away from Car A: 280m=0.28km280 \, \text{m} = 0.28 \, \text{km}
  2. Determine the time for Cars A and C to meet: The relative speed of Cars A and C is the sum of their speeds because they are moving towards each other: Relative speed=54km/h+72km/h=126km/h\text{Relative speed} = 54 \, \text{km/h} + 72 \, \text{km/h} = 126 \, \text{km/h} The time taken for Cars A and C to meet is: Time=Distance between A and CRelative speed=0.28km126km/h=0.281260.00222hours\text{Time} = \frac{\text{Distance between A and C}}{\text{Relative speed}} = \frac{0.28 \, \text{km}}{126 \, \text{km/h}} = \frac{0.28}{126} \approx 0.00222 \, \text{hours} This is equivalent to 0.00222×60=0.133minutes0.00222 \times 60 = 0.133 \, \text{minutes}, or roughly 8 seconds.

  3. Determine the speed of Car B: Car B needs to cover the distance between itself and Car A (which is 0.1 km) in the same time (0.00222 hours) to meet Car A and Car C simultaneously. Let vBv_B be the speed of Car B. The time it takes Car B to meet Car A is: Time=0.1kmvB=0.00222hours\text{Time} = \frac{0.1 \, \text{km}}{v_B} = 0.00222 \, \text{hours} Solving for vBv_B: vB=0.10.0022245km/hv_B = \frac{0.1}{0.00222} \approx 45 \, \text{km/h} However, Car B is already traveling at the same speed as Car A, meaning it doesn't need to catch up to Car A in this particular scenario. Therefore, its speed for matching

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Math Problem Analysis

Mathematical Concepts

Relative Speed
Distance and Time Conversion
Algebra

Formulas

Relative speed (same direction) = |speed of car A - speed of car B|
Relative speed (opposite direction) = speed of car A + speed of car C
Time = Distance / Speed

Theorems

None

Suitable Grade Level

Grades 10-12