on a 60 km track, a train travels the first 30 km with a uniform speed of 30km/h. How fast must train travel the next 30km so as average 40km/h for the entire trip?
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for the first part of the journey,
speed=30km/h
distance=30km
time=1. (i)
for the second part
speed =xkm/h
distance =30km
time = 30/x. (ii)
total time= 60%40=3/2
adding i and ii
3/2=1+30/x
x=61/3km/h
therefore the train has to travel the next 30km at the speed of 20.3km/h
speed=30km/h
distance=30km
time=1. (i)
for the second part
speed =xkm/h
distance =30km
time = 30/x. (ii)
total time= 60%40=3/2
adding i and ii
3/2=1+30/x
x=61/3km/h
therefore the train has to travel the next 30km at the speed of 20.3km/h
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