Math Problem Statement

A train leaves union station for central station, 216km away, at 9am. One hour later, a train leaves central station for union station. They meet at noon. If the second train had started at 9am and the first train at 10:30am, they would still have met at noon. Find the speed of each train.

Solution

We can solve this problem by setting up equations based on the distances traveled by both trains.

Step 1: Define the Variables

Let:

  • v1v_1 be the speed of the first train (leaving Union Station).
  • v2v_2 be the speed of the second train (leaving Central Station).
  • The total distance between Union Station and Central Station is 216km216 \, \text{km}.

Step 2: Scenario 1 - Actual Departure Times

In the actual scenario, the first train departs at 9:00 AM from Union Station, and the second train departs at 10:00 AM from Central Station. They meet at 12:00 PM.

Time Traveled by the Trains:

  • The first train travels for 3 hours (from 9:00 AM to 12:00 PM).
  • The second train travels for 2 hours (from 10:00 AM to 12:00 PM).

Distances Traveled:

  • The first train travels a distance of 3v13v_1.
  • The second train travels a distance of 2v22v_2.

Since they meet, the sum of the distances traveled by both trains must equal the total distance between the stations: 3v1+2v2=216km3v_1 + 2v_2 = 216 \, \text{km}

Step 3: Scenario 2 - Hypothetical Departure Times

In the second scenario, the second train starts at 9:00 AM, and the first train starts at 10:30 AM. They still meet at noon.

Time Traveled by the Trains:

  • The second train travels for 3 hours (from 9:00 AM to 12:00 PM).
  • The first train travels for 1.5 hours (from 10:30 AM to 12:00 PM).

Distances Traveled:

  • The second train travels a distance of 3v23v_2.
  • The first train travels a distance of 1.5v11.5v_1.

Again, since they meet, the sum of the distances traveled must be 216 km: 1.5v1+3v2=216km1.5v_1 + 3v_2 = 216 \, \text{km}

Step 4: Solve the System of Equations

Now, we have two equations:

  1. 3v1+2v2=2163v_1 + 2v_2 = 216
  2. 1.5v1+3v2=2161.5v_1 + 3v_2 = 216

We can solve this system of equations to find v1v_1 and v2v_2.

First, let's solve the first equation for v1v_1: v1=2162v23v_1 = \frac{216 - 2v_2}{3}

Now substitute this into the second equation: 1.5(2162v23)+3v2=2161.5 \left(\frac{216 - 2v_2}{3}\right) + 3v_2 = 216 Simplify the equation: 0.5(2162v2)+3v2=2160.5(216 - 2v_2) + 3v_2 = 216 108v2+3v2=216108 - v_2 + 3v_2 = 216 2v2=1082v_2 = 108 v2=54km/hv_2 = 54 \, \text{km/h}

Now substitute v2=54v_2 = 54 into the first equation: 3v1+2(54)=2163v_1 + 2(54) = 216 3v1+108=2163v_1 + 108 = 216 3v1=1083v_1 = 108 v1=36km/hv_1 = 36 \, \text{km/h}

Final Answer:

  • The speed of the first train is 36km/h36 \, \text{km/h}.
  • The speed of the second train is 54km/h54 \, \text{km/h}.

Would you like further details or clarification?


Here are 5 related questions to expand your understanding:

  1. How would the meeting time change if both trains started at 9:30 AM?
  2. What if the distance between the stations was 300 km? How would the speeds change?
  3. What would happen if one train traveled 10 km/h faster than the other?
  4. Could you find the time they meet if both trains had the same speed?
  5. What if a third train left 1 hour later at a different speed—where would it meet the others?

Tip: In distance-speed-time problems, always break down each part into distance and time traveled to set up a system of equations.

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Math Problem Analysis

Mathematical Concepts

Algebra
Distance-Speed-Time Relationships
Systems of Linear Equations

Formulas

Distance = Speed × Time
System of Equations: 3v_1 + 2v_2 = 216 and 1.5v_1 + 3v_2 = 216

Theorems

Linear Equations

Suitable Grade Level

Grades 8-10