Math
posted by Debbie on .
The The speed of a passenger train is 12 mph faster then the speed of a freight train. The passenger train travels 270 miles in the same time it takes the freight train to travel 210 miles. Find the speed of each train.

If we take the speed of the freight train to be x, and the speed of the passenger train to be y, we get that:
1)y=x+12
2)270/y=210/x
So if we replace y in the second equation by the y we found in the forst equation, we get that:
270/(x+12)=210/x
=>210*(x+12)=270x
=>60x=2520
=>x=42
=>y=54
So the freight train moves at 42mph and the passenger train moves at 54mph 
Let the speed of the freight train be x mph
then the speed of the passenger train is x+12 mph
Time for freight train = 210/x
time for passenger train = 270/(x+12)
but they are equal so....
270/(x+12) = 210/x
crossmultiply and solve.
Let me know what you got.