Math Problem Statement

A and B are two stations 560 km apart. A train starts from A at 7a.m. and travels towards B at 80 km/h. Another train starts from B at 9 a.m. and travels towards A at 120 km/h. When will they meet each other

Solution

We can solve this problem step by step.

Step 1: Calculate the distance covered by the first train before the second train starts.

  • Train A starts at 7 a.m. and travels at 80 km/h.
  • Train B starts at 9 a.m., meaning Train A has 2 hours of head start.

Distance covered by Train A in 2 hours: Distance=Speed×Time=80km/h×2hours=160km.\text{Distance} = \text{Speed} \times \text{Time} = 80 \, \text{km/h} \times 2 \, \text{hours} = 160 \, \text{km}.

So, Train A is 560 - 160 = 400 km away from B when Train B starts at 9 a.m.


Step 2: Relative speed of the trains.

  • Train A travels towards B at 80 km/h.
  • Train B travels towards A at 120 km/h.
  • The relative speed of the trains (since they are moving towards each other) is: Relative Speed=80km/h+120km/h=200km/h.\text{Relative Speed} = 80 \, \text{km/h} + 120 \, \text{km/h} = 200 \, \text{km/h}.

Step 3: Time taken for the trains to meet.

The trains now need to cover the 400 km gap between them at a combined speed of 200 km/h.

Time to meet: Time=DistanceRelative Speed=400km200km/h=2hours.\text{Time} = \frac{\text{Distance}}{\text{Relative Speed}} = \frac{400 \, \text{km}}{200 \, \text{km/h}} = 2 \, \text{hours}.


Step 4: Find the meeting time.

  • Train B starts at 9 a.m., and they meet 2 hours later.
  • Therefore, they will meet at: 9a.m.+2hours=11a.m..9 \, \text{a.m.} + 2 \, \text{hours} = 11 \, \text{a.m.}.

Final Answer:

The two trains will meet at 11 a.m..


Would you like a detailed explanation of the concepts used here, or do you have any questions? Here are 5 related problems you can explore:

  1. What if the trains started at the same time but with their respective speeds?
  2. How far from Station A will they meet?
  3. What would happen if Train B traveled at 100 km/h instead of 120 km/h?
  4. How long would it take if Train A's speed was reduced to 60 km/h?
  5. What is the total distance covered by both trains before meeting?

Tip: When solving problems involving relative speed, always determine whether the objects are moving towards or away from each other, as it affects the combined speed.

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Math Problem Analysis

Mathematical Concepts

Relative Speed
Linear Distance
Time and Distance Calculations

Formulas

Distance = Speed × Time
Relative Speed = Speed1 + Speed2 (when moving towards each other)
Time = Distance ÷ Speed

Theorems

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Suitable Grade Level

Grades 6-8