The same tidal effect... that is a tough question since the tides depend a lot on geography and the inertia of the moving water.
But generally, you can say, it would have the same gravity force acting on the water, if ...
And density would have ...
Should I do your homework now? :lol:
As formula, simple simple simple...
[math]F = \frac{G M m}{r^2}[/math]
And of course because of that:
[math]\frac{1}{{r_l}^2} = \frac{1}{10 {r_2}^2} \Leftrightarrow {r_l}^2 = 10 {r_2}^2 \Leftrightarrow \frac{r_l}{\sqrt{10}} = {r_2} [/math]