The answer is 1300 ft.
1 : 400 = 3 : 1200 = 3.25 : 1300
(The rate you were giving was 400 miles traveled per hour or 1:400. Then you had to figure out how far you would travel if you went for 3 hours and 15 minutes. 15 minutes of an hour can also be written as 1/4 of an hour or 0.25, so all you have to do is multiply both numbers by 3.25 in the ratio given and you will get you answer: 3.25 : 1300, simplified 1300 ft.)
