Ok so, ignore what I said previously.
The question states that a particle is attached to the middle of the spring. Think of this particle now decomposing the spring into two springs of equal length
a.
Now in our situation, we have the following diagram:
Obviously,
5a is the height of the room, and let us denote our wanted distance by
x.
Naturally, the particle (shown as the box) is below the half-way point of AB.
Note that with springs, they can be either compressed or extended. In either case, they have tension in them that make them want to return to their natural state.
Let us suppose that both strings are
extended. Therefore both strings do their best to return to their natural length. The top string tries to pull the particle up with its own tension of
T1, and the bottom string tries to pull the particle down with its own force of
T2.
The extension in the top string is
e1=x−a.
The extension in the bottom string is
e2=(5a−x)−a=4a−xThen you can work out the tensions in both springs by applying the formula
T=lλe where
λ is the same in both springs.
Then proceed to solve for
x by equating the appropriate forces.