If you were to triple the size of the earth (r = 3r⊕) and double the mass of the earth (m = 2m⊕), how much would it change the gravity on the earth (fg = xfg⊕)?

Decreased by a factor of 4.5

Explanation:

"We have Newton formula for attraction force between 2 objects with mass and a distance between them:

where is the gravitational constant on Earth. are the masses of the object and Earth itself. and R distance between, or the Earth radius.

So when R is tripled and mass is doubled, we have the following ratio of the new gravity over the old ones:

Since and

So gravity would have been decreased by a factor of 4.5