Average Speed Of The Train
Average speed is a measure of the overall rate at which an object or person has covered a certain distance over a given period of time. It is calculated by dividing the total distance traveled by the total time taken.
Average Speed = Total Distance / Total Time
For example, if a car travels 200 kilometers in 4 hours, the average speed would be:
Average Speed = 200 km / 4 hours = 50 km/h
Average speed provides an indication of how fast or slow an object or person is moving on average, considering the entire journey. It is important to remember that average speed does not provide information about the specific variations in speed during the travel; it represents an overall measure of the rate of travel over the entire duration.
Solution
We need to calculate the time it takes for the train to travel the first 30 km and the remaining 90 km.
Let's denote the speed of the train for the remaining part as v km/h.
Time taken to travel the first 30 km:
Time = Distance / Speed
Time = 30 km / 30 km/h
Time = 1 hour
Now, let's calculate the time taken to travel the remaining 90 km:
Time = Distance / Speed
Time = 90 km / v km/h
Time = 90/v hours
The total time taken for the entire trip is the sum of the time taken for the first 30 km and the time taken for the remaining 90 km:
Total Time = 1 hour + 90/v hours
Total Time = (v + 90)/v hours
To average 60 km/h for the entire trip, the total time taken should be:
Total Time = Total Distance / Average Speed
Total Time = 120 km / 60 km/h
Total Time = 2 hours
Setting the two expressions for the total time equal to each other:
(v + 90)/v = 2
Now, let's solve this equation for v:
(v + 90) = 2v
90 = v
Therefore, the train must travel the remaining part of the journey at a speed of 90 km/h in order to average 60 km/h for the entire trip.
Summary
On a 120 km long track, a train travels the first 30 km with a uniform speed of 30 km/h. How fast must the train travel for the rest part of the journey so as to average 60 km/h for the entire trip?
On a 120 km long track, a train travels the first 30 km with a uniform speed of 30 km/h. The train must travel 90 km/hr for the rest part of the journey to an average of 60 km/h for the entire trip.
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