Answer: the rate of the passenger train is 100 mph.
Step-by-step explanation:
Let x represent the rate of the passenger train.
The rate of the freight train was 10 miles per hour slower than the rate of the passenger train. It means that the rate of the freight train is (x - 10) mph
The passenger train traveled 100 miles. It means that the time it took travel 100 miles is
100/x
In the same amount of time, it took a freight train to travel 90 miles. It means that the time it took travel 90 miles is
90/(x - 10)
Since the time is the same, then
100/x = 90/(x - 10)
Cross multiplying, it becomes
100(x - 10) = 90x
100x - 1000 = 90x
100x - 90x = 1000
10x = 1000
x = 100 mph
