Two masses are attracted by a gravitational force of 0.55 N.

(a) What will the force of attraction be if the distance between the two masses doubled?

since F is inversely proportional to the square of the distance,

if F = GMm/r^2 then if r is doubled,
F' = GMm/(2r)^2 = 1/4 GMm/r^2 = 1/4 F