Object A experiences a gravitational force due to object B. How would that force change if the separation distance is halved, mA triples, and mB is reduced to one quarter of its original value?

1 answer

You know that

F = GMm/r^2

so, what happens to F if r is replaced by r/2?

F' = GMm/(r/2)^2 = 4GMm/r^2 = 4F

use the same technique when replacing the other quantities.