A truck driven by George makes its journey in two parts.
In the first part, its speed is 82 km/h and it travels for 4 hours.
Then, George has a break at a petrol station for 20 minutes.
In the second part, George travels at a speed of 70 km/h for 3 hours.
What is his average speed?
To solve this problem, we'll follow these steps:
- Step 1: Calculate the distance for each part of the journey.
- Step 2: Find the total distance traveled.
- Step 3: Convert all time to hours and include the break time.
- Step 4: Calculate the average speed using the formula for average speed.
Let's calculate each step:
Step 1: Calculate the distances:
For the first part of the journey:
Speed = 82 km/h, Time = 4 hours
Distance = Speed × Time = 82×4=328 km
For the second part of the journey:
Speed = 70 km/h, Time = 3 hours
Distance = Speed × Time = 70×3=210 km
Step 2: Total distance traveled:
Total Distance = Distance of first part + Distance of second part
Total Distance = 328+210=538 km
Step 3: Calculate total time including the break:
Total time driving = 4 hours (first part) + 3 hours (second part) = 7 hours
Break time = 20 minutes = 6020=31 hours
Total time = Driving time + Break time = 7+31=322 hours
Step 4: Calculate the average speed:
Average speed vavg=Total timeTotal distance
Average speed vavg=322538=538×223=22538×3=221614
Simplifying 221614: Average speed ≈ 73.36 km/h
Therefore, the average speed of George's truck for the entire journey, including the break, is 73.36 km/h.