Two slabs with square cross section of different materials (1,2) with equal sides $(l)$ and thickness ${d_1}$ and ${d_2}$ such that ${d_2} = 2{d_1}$ and $l > {d_2}$. Considering lower edges of these slabs are fixed to the floor, we apply equal shearing force on the narrow faces. The angle of deformation is ${\theta _2} = 2{\theta _1}$. If the shear moduli of material 1 is $4 \times {10^9}\;{\rm{N}}/{{\rm{m}}^2}$, then shear moduli of material 2 is $x \times {10^9}\;{\rm{N}}/{{\rm{m}}^2}$, where value of $x$ is __________.