posted by kay .
the speed of a passenger train is 18mph faster than the speed of a freight train. The passenger train travels 310 miles in the same time it takes the freight train to travel 220 miles. Find the speed of each train passenger train mph and freight train mph
Because the time used to travel is the same (regardless of the difference in distance) we can set the freight trains time equal to the passenger train's time.
Let's start off with the freight train. The distance is 310. It says the speed is 18 mph faster than the speed of the freight train. So I pets set a variable: X, where X is the speed of the freight train. Therefore the time if the freight train, distance over time, can be substituted with 310mph/X+18
now the time of the freight train. The distance is 220, and the speed is X. Therefore, the time is distance over speed, which you can subatitute into 220/X
Now, set the time equal.
319/X+18 = 220/X
Solve for x, and you'll find the freight train is 44 mph, and the pass train is 62 mph.