The weight of an object varies inversely as the square of its distance from the center of the Earth. If an object at sea level (3978 mi from the center of the earth) weighs 220 lb, find its weight when it's 200 mi above the surface of the earth.
No! If we're going to be consistent we have to use 3,978 miles plus 200 miles (= 4178 miles) as the distance the object is from the center of the earth. Remember, the problem states that the object is 200 miles above the surface of the earth, not the center of the earth.
w = 3,481,386,480 lb mi-2/(4178 mi)2
w = 3,481,386,480 lb mi-2/(17455684 mi2)
w = 199.441 lb