Five equal resistances are connected in a network as shown in figure.

$(3)$

It is balanced wheat stone bridge

So, we know that

$\mathrm{R}_{1} \mathrm{R}_{\mathrm{A}}=\mathrm{R}_{2} \mathrm{R}_{3}$

$\frac{\mathrm{R}_{1}}{\mathrm{R}_{2}}=\frac{\mathrm{R}_{3}}{\mathrm{R}_{4}}$

$\operatorname{Req}=\frac{2 R \times 2 R}{2 R+2 R}$

$\frac{4 R^{2}}{4 R} \Rightarrow R$