Five resistors are connected as shown in the diagram. The equivalent resistance between A and B is

Solution:

Since the given bridge is balanced, hence there will be no current through $9\Omega$ resistance. This resistance has no effect and must be ignored in the calculations.

${\mathrm{R}}_{\mathrm{AB}}=\frac{9\times 18}{27}=6\mathrm{\Omega }$