The weight of an apple near the surface of the Earth is 1 N. What is the weight of the Earth in the gravitational field of the apple?

1 N

Explanation:

According to Newton's 3rd law and also Newton's gravitational law, the force that the Earth exert on the apple would be equal (and in opposite direction) with the force that the apple exert on the Earth, in this cast it's the gravitational field of the apple. So it's also 1N.