It took the train 4 hours to travel the 400 miles.
If it takes 1 hour to travel 100 miles, then we are finding how much it takes to travel 400. 400 hundred is four times the amount of 100, so if we are converting 100 to 400, then we must also convert 1 hour to x hours using the same process. Since 1 times 4 is 4, then we know that it took 4 hours to travel the 400 miles.
100/1 = 400/4 ---> both of the fractions are the same/they have the same ratio
I hope this helped, and I wish you much luck on your math journey!
