At sea, the distance d to the horizon is directly proportional to the square root of the elevation e of the observer. if a person who is 36 feet above the water can see 7.4 miles, find how far a person 49 feet above the water can see.

The problem says that the distance D to the horizon is directly proportional to the square root of the elevation E of the observer, so:

 The person who is 36 feet above the water ⇒ √36=6 

 A person 49 feet above the water ⇒ √49=7

 So, by proportions, you have:

 (7/6)x7.4= 8.63 miles

 Therefore, the answer is: a person 49 feet above the water can see 8.63 miles