Grounded conductor within a charged shell

[anirudh30]

In a question there are two conducting shells of radii a and b (a<b),the outer shell is given a charge Q . And the inner shell is grounded then the potential of that shell was equated to zero and its charge was assumed q.
And it resulted in an equation
KQ/b + Kq/a = 0 this gave q = -(a/b)Q
But when a conductor is grounded then the conductor can be taken as ground itself and then it will be equivalent of saying that we charged the ground with -(a/b)Q charge as the inner shell has this much charge.?
Please help me clear it.

 

[Yitzach]

Ground is a large resivor of charges that can be moved where ever needed. The rest of the ground has a charge of (a/b)Q as the opposite is now in that little ball.

 

[anirudh30]

Yeah thanks!