Answer:
3/8 R
Explanation:
If all of the resistor values are R, the circuit consists of two parallel branches, each of which is R in parallel with 3R. That branch resistance is ...
(R)(3R)/(R +3R) = 3/4 R
The two equal branches in parallel reduce this by half to ...
(1/2)(3/4 R) = 3/8 R
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Because the front face of the "cube" and the rear face are identical, there is no current flow between the faces at the top and bottom right edges. There is no voltage difference across those two resistors, hence no current flow. They can be ignored for the purpose of the equivalent circuit.
