SOLUTION: An express train is 50 kph faster than the freight train. If it takes 2 hour less for the express train to travel 600 km as compare to the freight train, how fast is the express tr

Question 1169435: An express train is 50 kph faster than the freight train. If it takes 2 hour less for the express train to travel 600 km as compare to the freight train, how fast is the express train?
Found 2 solutions by Boreal, MathTherapy:
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
distance=v*t
v=freight and it takes t hours so the speed is 600/t
for the express it takes 600/(t-2) hours
600/(t-2)-50=600/t
multiply by t(t-2)
600t-50t^2+100t=600t-1200
0=50t^2-100t-1200
0=t^2-2t-24=(t-6)(t+4)
only positive root is t=6 hours
so the the velocity for the express train is 100 kph and the express is 150 kph and takes 4 hours, 2 hours fewer, to go the same distance.
Answer by MathTherapy(10551) (Show Source): You can put this solution on YOUR website!
An express train is 50 kph faster than the freight train. If it takes 2 hour less for the express train to travel 600 km as compare to the freight train, how fast is the express train?

You don't NEED to find time as the other person suggests!
Let the express train's speed be S
Then the freight train's speed = S - 50
We then get the following TIME equation:
------ Factoring out GCF, 2, in numerator
300(S - 50) + S(S - 50) = 300S ----- Multiplying by LCD, S(S - 50)

S - 150 = 0 OR S + 100 = 0
Speed of express train, or OR S = - 100 (ignore)
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