Gravitational force f exists between oint objects a and b seperated by distance r. if the mass of a is doubled and the distance r is tripled, what is the new gravitational force between a and b?

-- Doubling one mass doubles the product of the masses, and
doubles the strength of the gravitational forces between them.

-- Tripling the distance between them changes the strength of the
gravitational forces between them by the factor of

                       1 / 3²  =  1 / 9 .

-- The new gravitational force between the objects is

                       ( 2 / 9 )  =  22.2%

of the strength of the original gravitational force.

If your workout exceeds an hour you should substitute "a sports drink" for water.hope my answer has you : )