On a 120km track, a train travels the first 30 km at a uniform speed of 30km/hr. How fast must the train travel the next 90 km so as to average 60 km/hr for the entire trip?
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Answered by
17
Speed of the train in the first 30 km, v1 = 30 km/h
Speed of the train in the next 90 km, v2 (to be determined)
Average speed = 60 km/h = (v1 + v2)/2
= (30 km/h + v2)/2
⇒ v2 = 90 km/h
Speed of the train in the next 90 km, v2 (to be determined)
Average speed = 60 km/h = (v1 + v2)/2
= (30 km/h + v2)/2
⇒ v2 = 90 km/h
Answered by
17
hey
as the total distance = 120 km
average speed = 60 kmph
=> total time duration = 120 / 60 = 2 hours
time taken for the first 30 km = 30 km /30 kmph = 1 hours
Hence, time remaining to cover the remaining 90 km = 2 hrs - 1 hrs = 1 hour
=> speed during 90 km = 90 kmph
Hope it helps to you.
as the total distance = 120 km
average speed = 60 kmph
=> total time duration = 120 / 60 = 2 hours
time taken for the first 30 km = 30 km /30 kmph = 1 hours
Hence, time remaining to cover the remaining 90 km = 2 hrs - 1 hrs = 1 hour
=> speed during 90 km = 90 kmph
Hope it helps to you.
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