Two bodies of mass m and 9m are placed at a distance R. The gravitational potential on the line joining the bodies where the gravitational field equals zero, will be (G = gravitational constant ) :

$-\frac{16Gm}{R}$

$\text{Let Gravitational field is zero at a distance x from mass m then } \frac{G.m}{x^2} = \frac{G.9m}{(R-x)^2} \Rightarrow R - x =  3x$

$ \Rightarrow x = \frac{R}{4}$

$\text{potential at this point is } V = \frac{-Gm}{R/4} + \frac{-9Gm}{3R/4} =\frac{-16Gm}{R}$