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An express train makes a run of 240 km at a certain speed. Another train whose speed is 12 km/hr less takes an hour longer to cover the same distance.Find

the original speed of the train.


total distance = 240 km
let speed = x km/hr
therefore time = 240/x hrs
new speed = x-12 km/hr
therefore time = 240/x-12 hrs
given difference = 1 hr
therefore 240/x-12 - 240/x=1
240x-240x+2880/x2-12x =1
2880 = x2-12x
by completing the squares
x=60 or x = -48
speed is non negetive 
therefore original speed of train = 60 km/hr

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