Final answer:
To find the average speed, total distance traveled is divided by total time taken. For a journey of 6 km at 50 km/h and another 6 km at 90 km/h, the average speed is calculated to be approximately 64.3 km/h, which does not match the provided options.
Step-by-step explanation:
Finding the Average Speed
To determine the average speed for the entire journey, we need to consider the total distance traveled and the total time taken to cover that distance. The formula for average speed is:
Average Speed = Total Distance / Total Time
First, calculate the time taken for each part of the journey:Time for first 6.0 km at 50 km/h = Distance / Speed = 6.0 km / 50 km/h = 0.12 hoursTotal time taken is 0.12 hours + 0.0667 hours = 0.1867 hours. traveled is the sum of both parts of the journey, which is 6.0 km + 6.0 km = 12.0 km.
Now, calculate the average speed using the formula mentioned above:Average Speed = Total Distance / Total Time = 12.0 km / 0.1867 hours ≈ 64.3 km/h
Based on our calculations, none of the options A. 70 km/h, B. 75 km/h, C. 80 km/h, D. 85 km/h match our result of approximately 64.3 km/h. Therefore, if these are the only available options, the question may contain a mistake or our calculations may need to be reviewed.