Question

An object weighs 3 lb. at 10 earth radii from its center. What is the object's weight on the earth's surface?

Answer 1

The weight is the same `3lb`. See explanation.

Explanation:

If by weight you mean the physical value measured in `lb` (or `kg`) usually called mass, then this value does not depend on a place where object is located. Object's mass would be the same everywhere even if you put it on Mars or the Sun.

The value which changes is the gravitational force. In your example it is `10^2=100` times greater on the Earth's surface than in the point `10` Earth's radii from its center.