A train travels in a straight line at a constant speed of 60 km/h for a particular distance d and then travels another distance equal to 2d in the same direction at a constant speed of 80 km/hr in the same direction as it was in the it was previously going a) What is the average speed of the train during the whole journey
Answers
Answer :-
Average Speed of the train for the whole journey is 72 km/h .
Explanation :-
We have :-
→ 1st distance = d
→ Speed for 1st distance = 60 km/h
→ 2nd distance = 2d
→ Speed for 2nd distance = 80 km/h
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From the question, we can understand that the train travels in the same direction throughout it's whole journey .
Firstly, we have to calculate the time taken by the train to cover both the distances .
Time taken in 1st case :-
= Distance/Speed
= (d/60) hrs
Time taken in 2nd case :-
= Distance/Speed
= 2d/80
= (d/40) hrs
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Average Speed :-
= Total distance/Total time
= [d + 2d]/[d/60 + d/40]
= 3d/[(2d + 3d)/120)]
= 3d/[5d/120]
= 3d/[d/24]
= (3d × 24)/d
= 72 km/h
Given :-
A train travels in a straight line at a constant speed of 60 km/h for a particular distance d and then travels another distance equal to 2d in the same direction at a constant speed of 80 km/hr in the same direction as it was in the it was previously going
To Find :-
Average speed
Solution :-
◼ I n C a s e 1 :-
⮆ Time = Distance/Speed
⮆ Time = d/60
◼ I n C a s e 2 :-
⮆ Time = Distance/Speed
⮆ Time = 2d/80
Average speed = Total distance/Total time
⮆ Total distance covered = d + 2d
⮆ Total distance covered = 3d
⮆ Total time taken = d/60 + 2d/80
⮆ Total time taken = 4d + 6d/240
⮆ Total time taken = 10d/240
⮆ Total time taken = d/24
Using above formula
⮆ Average speed = 3d/(d/24)
⮆ Average speed = 3d/1 × 24/d
⮆ Average speed = 72d/d
⮆ Average speed = 72 km/h