What would be the acceleration of gravity of a planet with four times the mass of Earth but twice the radius?

- - Multiplying the mass by 4 multiplies the acceleration of gravity by 4.

- - Doubling the radius multiplies the acceleration of gravity by (1/2²) = 1/4.

- - Doing both multiplies the acceleration of gravity by (4 / 4) = 1.

It doesn't change. The acceleration of gravity on that planet

would be the same as it is on Earth.