On a 100km track ,a train travels the first 30 km at a uniform speed of 30 km /hr .How fast must the the train travel for the next 70 km as to average speed 40 km/hr for the entire trip
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At average speed of 40km/h for the entire journey:
Time = Distance ÷ Speed = 100 ÷ 40 = 2.5 hours
Time taken for the first part of the journey:
Time = Distance ÷ Speed = 30 ÷ 30 = 1 hour
Time left for the rest of the 70km:
2.5 hour - hour = 1.5 hour
Speed needed for the 70km:
Speed = Distance ÷ Time = 70 ÷ 1.5 = 45.67 km/h
Answer: The train must travel at 45.67 km/h for the 70 km.
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