On a 120 km track ,a train travels 30 km at a uniform speed of 30 km/hr. How fast must the train travel the next 90 km so as to get the average speed of 60km/hr for entire trip ?
pratyush4211:
does ans is 45.5 km/h
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Track Length=120 km
30 km at=30 km/h
Time=Distance/speed
Time=30/30
Time=1 hour
Let it travel 90 km at=x km/h
Time=90/x hour
AVERAGe Speed=60 km/h
AVERAGe speed=Total Distance/Total Time
120/1+90/x=60
120/x+90/x=60
120x/x+90=60
120x=60(x+90)
120x=60x+5400
120x-60x=5400
60x=5400
x=5400/60
x=90 km/h
Speed Should be=90 km/h
Track Length=120 km
30 km at=30 km/h
Time=Distance/speed
Time=30/30
Time=1 hour
Let it travel 90 km at=x km/h
Time=90/x hour
AVERAGe Speed=60 km/h
AVERAGe speed=Total Distance/Total Time
120/1+90/x=60
120/x+90/x=60
120x/x+90=60
120x=60(x+90)
120x=60x+5400
120x-60x=5400
60x=5400
x=5400/60
x=90 km/h
Speed Should be=90 km/h
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