Final answer:
To find the average speed for the train's journey of 80 km, we calculated the time taken for each segment separately and then divided the total distance by the total time, which resulted in an average speed of 32 km/hr, not matching any provided options. Option B is the nearest correct answer.
Step-by-step explanation:
The question asks us to calculate the average speed of a train on a journey where different segments are traveled at different speeds. The total distance of the journey is 80 km: 60 km at 40 km/hr and the remaining 20 km at 20 km/hr. To find the average speed, we need to consider the total distance traveled and the total time taken for the complete journey.
First, we calculate the time taken to cover the first 60 km at 40 km/hr:
- Time = Distance / Speed = 60 km / 40 km/hr = 1.5 hours
Next, we calculate the time taken to cover the remaining 20 km at 20 km/hr:
- Time = Distance / Speed = 20 km / 20 km/hr = 1 hour
Now, we can find the total time for the journey:
- Total time = 1.5 hours + 1 hour = 2.5 hours
Finally, to find the average speed, we divide the total distance by the total time:
- Average speed = Total distance / Total time = 80 km / 2.5 hours = 32 km/hr
Therefore, the average speed for the whole journey is 32 km/hr, which is not one of the options provided. It appears there might be a mistake in the options given, as the calculated average speed doesn't match any of them.