Hello!
Right now, we know that the train has travelled 204 miles in exactly four hours. In order to find how many miles the train travels per hour, we can divide 204 by 4:
204/4 = 51
The train is traveling 51 miles per hour. The train still needs to travel 3 1/2 more hours. To find how many miles it will travel, we can multiply 51 by 3, and add 51/2.
51 x 3 = 153
51/2 = 25.5
153 + 25.5 = 178.5
The train travels 178.5 miles in the additional 3 1/2 hours. Now, we will add this number to the number of miles that the train has already travelled in four hours:
178.5 + 204 = 382.5
The train will travel 382.5 miles in 7 1/2 hours.
I hope this helps you! Have a lovely day!
- Mal