What is the total resistance across A and B in the circuit

Question

Answer 1

There will not be any current flowing through CD , so inner triangle would not be used for calculation of resistance.

R_AB  = ( R/2 + R) in parallel with R

R_AB  = ( 3R/2 ) in parallel with R  =  { (3R/2) R }/ {  3R/2 + R }

R_AB  =  { (3R/2) R }/ {  5R/2 }  = (3R)/5