When royce was 10 years old, he had a mass of 30 kg. By the time he was 16 years old, his mass increased to 60 kg. How much larger is the gravitational force between royce and the earth at age 16 compared to age 10?

I think it would be doubled.

F = ma, m has doubled, a is still g. So Strat is right (assuming he hasn't moved up a mountain or from the pole to the equator or whatever).

You can use that equation to work out how many Newtons he's weight has changed by.

I was tempted to say, " if he was 19, it would triple" I caught myself.