A Freight train is traveling 30 miles per hour. An automobile starts out from the same place 1 hour later and overtakes the train in 3 hours. What was the rate of the automobile?

Answer 1

the train went for 4 hours at 30 mph, so it went 120 miles
the car also went 120 miles but only took 3 hours , let its rate be x mph

so solve:
3x = 120