Short Circuit

The equivalent circuit of the three resistors is a parallel circuit as shown above. Therefore, the resistance between $A$ and $B$ is:

$R_{AB} = \dfrac{1}{\frac{1}{30} + \frac{1}{30} +\frac{1}{30}} = \dfrac{1}{\frac{1}{10}} = \boxed{10} \space \Omega$