A car travels 120 miles at an average speed of 40 mph, then continues for another 180 miles at 60 mph. What is the car’s average speed for the entire trip? - Treasure Valley Movers

Title: How to Calculate Average Speed for a Two-Part Road Trip | Fast and Efficient Travel

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When planning road trips, determining average speed is essential for better time management and trip planning. One common scenario involves multiple segments with varying speeds—like a car traveling 120 miles at 40 mph, then continuing another 180 miles at 60 mph. Understanding the total journey and total time helps calculate the overall average speed accurately. In this article, we’ll break down how to compute the average speed for the entire trip, why it’s more than just a simple mean, and how to find the correct figure for smoother travel forecasts.

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What Is Average Speed?

Average speed is defined as the total distance traveled divided by the total time taken, not the arithmetic mean of speeds. This matters because speed changes across different segments—longer periods at lower speeds drag down the overall average, even if a segment was completed quickly.

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The Journey Breakdown

In this example:

• First leg: 120 miles at 40 mph
  
• Second leg: 180 miles at 60 mph

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Step 1: Calculate Time for Each Segment

Segment 1:
Time = Distance ÷ Speed
Time₁ = 120 miles ÷ 40 mph = 3 hours

Segment 2:
Time₂ = 180 miles ÷ 60 mph = 3 hours

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Step 2: Total Distance and Total Time

• Total distance: 120 + 180 = 300 miles
  
• Total time: 3 + 3 = 6 hours

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Step 3: Calculate Average Speed

Average speed = Total distance ÷ Total time
Average speed = 300 miles ÷ 6 hours = 50 mph

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Why This Method Works