Question:medium

Two trains, A and B, start from stations X and Y, 300 km apart, and travel towards each other. Train A travels at 60 km/h, and Train B travels at 90 km/h. If Train A starts 1 hour earlier than Train B, how long will it take for the two trains to meet after Train B starts?

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Remember: For objects moving towards each other, use relative speed (sum of speeds). Account for head starts by adjusting the initial distance before applying the time formula.
Updated On: Jan 16, 2026
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Solution and Explanation

The objective is to calculate the meeting time of two trains traveling towards each other, considering their distinct departure times and speeds.

1. Problem Setup:
- Distance between stations X and Y = 300 km 
- Speed of Train A = 60 km/h 
- Speed of Train B = 90 km/h 
- Train A departs 1 hour before Train B 
- Let t be the time in hours Train B travels until the trains meet 
- Consequently, Train A travels for t + 1 hours

Core Principle: When two objects move towards each other, their combined distance covered equals the sum of their individual distances traveled. Thus, Total Distance = Distance covered by Train A + Distance covered by Train B

2. Equation Formulation: 
Assuming the meeting occurs t hours after Train B's departure: 
Distance covered by Train A = 60 × (t + 1) Distance covered by Train B = 90 × t 
The problem equation is: $ 60(t + 1) + 90t = 300 $

3. Equation Solution: 
Expanding the equation: $ 60t + 60 + 90t = 300 $ 
Combining terms: $ 150t + 60 = 300 $ 
Subtracting 60 from both sides: $ 150t = 240 $ 
Dividing by 150: $ t = \frac{240}{150} = 1.6 \, \text{hours} $

4. Time Conversion: 
$ 0.6 \, \text{hours} = 0.6 \times 60 = 36 \, \text{minutes} $ 
Therefore, the time elapsed after Train B starts is 1 hour and 36 minutes.

Conclusion: 
The two trains will intersect 1 hour and 36 minutes subsequent to Train B's departure.

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