To determine the average speed Dad needs to maintain during the second half of the trip, we first need to break down the journey into manageable parts. The total distance of the trip is 60 km, which means each half of the trip is 30 km. Since Dad wants an overall average speed of 140 km/h, we can calculate the total time he should take for the entire trip.
Calculating Total Time for the Trip
The formula for average speed is:
Average Speed = Total Distance / Total Time
Rearranging this gives us:
Total Time = Total Distance / Average Speed
Plugging in the values:
Total Time = 60 km / 140 km/h = 0.4286 hours (approximately 25.71 minutes)
Time Taken for the First Half
Now, let's calculate how long it takes to travel the first half of the trip at an average speed of 110 km/h:
Time = Distance / Speed
For the first half (30 km):
Time = 30 km / 110 km/h = 0.2727 hours (approximately 16.36 minutes)
Determining Remaining Time for the Second Half
Next, we need to find out how much time is left for the second half of the trip:
Remaining Time = Total Time - Time Taken for First Half
Remaining Time = 0.4286 hours - 0.2727 hours = 0.1559 hours (approximately 9.36 minutes)
Calculating Required Speed for the Second Half
Now, we can find out what speed Dad needs to maintain during the second half to meet his goal:
Speed = Distance / Time
For the second half (30 km):
Speed = 30 km / 0.1559 hours ≈ 192.5 km/h
Conclusion
To achieve an average speed of 140 km/h for the entire trip, Dad must drive at an average speed of approximately 192.5 km/h during the second half of the journey. This is significantly higher than the speed limit on most highways, so it’s essential to consider safety and legal regulations while planning the trip.
