Question

The distance between two bodies is r , if the mass of one is doubled , so the distance between them has to be X*r to make attraction force between them decreases to its half.

Answer 1

$\frac{m_1m_2}{r^2}\frac{1}{2} = \frac{2m_1m_2}{(Xr)^2} ; \\ X^2 = 4; \\ X = 2.$