Final answer:
The speed of the southbound boat is 4 miles per hour.
Step-by-step explanation:
To find the speed of the southbound boat, let's consider the distance traveled by each boat after 5 hours. Since the eastbound boat travels at a speed 1 mile per hour faster than the southbound boat, let's assume the speed of the southbound boat as x miles per hour. Therefore, the speed of the eastbound boat will be (x + 1) miles per hour.
Distance traveled by the southbound boat = speed x time = x * 5 = 5x miles
Distance traveled by the eastbound boat = speed x time = (x + 1) * 5 = 5x + 5 miles
According to the problem, after 5 hours, the boats are 25 miles apart. So, the equation becomes: 5x + 5 - 5x = 25. Solving this equation gives x = 4.
Therefore, the speed of the southbound boat is 4 miles per hour.