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If a train travels from Station A to Station B at a speed of 80 km/h and then returns from Station B to Station A at a speed of 60 km/h, what is the average speed of the train for the entire round trip?
Let the distance between station A and station B be "D". As we know that Speed(S) = Distance (D)/Time (t) So time(t1) from station A to station B will be : S=D/t 80 km/h = D/t1 t1 = D/80 hrs. Similarly, time(t2) from station B to station A will be : S = D/t 60 km/h = d/t2 t2 = D/60 hrs.Read more
Let the distance between station A and station B be “D”.
As we know that
Speed(S) = Distance (D)/Time (t)
So time(t1) from station A to station B will be :
S=D/t
80 km/h = D/t1
t1 = D/80 hrs.
Similarly, time(t2) from station B to station A will be :
S = D/t
60 km/h = d/t2
t2 = D/60 hrs.
Now,
Average Speed = Total Distance/ Total time
Total Distance = D+D
=2D
Total Time = t1+t2
=(D/80 + D/60) Hrs.
= (3D+4D/240) Hrs.
= 7D/240 Hrs.
Average Speed = Total Distance/ Total time
Average Speed = 2D÷7D/240
=2D×240/7D
=480/7 km/h
=68.57 km/h (approx.)
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