An object on the surface of the earth weighs 90 lb. at three earth radi above the surface it will weigh

acceleration due to gravity on surface of earth is given as

now at the surface of earth we know its value will be g = 9.8 m/s^2

it is given that we need to find the weight at height three earth radii above the surface

so we can say

now from above equation we can say that here the acceleration due to gravity is 1/16 times of the gravity at surface

So as we know that the weight is measured as

if gravity is decreased by 1/16 times then weight will also decrease by the same factor

So weight will be measured as

So its weight above the surface will 5.625 lb at that height

neither accurate nor precise.