A train travels 300 km at speed 100 km/h, then continues another 200 km at speed 80 km/h. What is the average speed for the entire journey? - Appcentric

Understanding the Context

Average speed is not simply the arithmetic mean of the two speeds. Instead, it measures total distance divided by total time. This approach captures the actual energy and time investment throughout the journey.

Step 1: Calculate travel time for each segment

• For the first 300 km at 100 km/h:
  Time = Distance ÷ Speed = 300 km ÷ 100 km/h = 3 hours
  
• For the next 200 km at 80 km/h:
  Time = 200 km ÷ 80 km/h = 2.5 hours

Step 2: Find total distance and total time

• Total distance = 300 km + 200 km = 500 km
  
• Total time = 3 hours + 2.5 hours = 5.5 hours

Step 3: Calculate average speed
Average speed = Total Distance ÷ Total Time
= 500 km ÷ 5.5 hours ≈ 90.91 km/h

Key Insights

Final Insight

So, the average speed for the entire train journey is approximately 90.91 km/h, not 90 km/h. This example highlights why average speed accounts for varying speeds—straightforward mean speed masks the true travel efficiency.

Understanding average speed helps travelers estimate arrival times more accurately and appreciate the dynamics of railway travel over mixed conditions.

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Meta Description: Learn how to calculate average speed for a train journey that travels 300 km at 100 km/h and 200 km at 80 km/h. Discover the correct method using total time over total distance.