Resistances RAF and RFE are in series combination. Therefore their equivalent resistance R′=RAF+RFE=3+3=6Ω. Now the resistance RAE and equivalent resistance R′ are in parallel combination. Therefore relation for their equivalent resistance
1
R′
=
1
R′
+
1
RAE
=
1
6
+
1
6
=
2
6
=
1
3
⇒R"=3Ω
We can calculate inthe same manner for RED,RAC,RDC etc.and finally the circuit reduces as shown in the figure. Therefore, the equivalent resistance between A and B =