Please answer this question in the given image of finding equivalent resistance

If you join battery between P and there will be no current on resitance having one terimal either at Q or S.

SO therewill be 3 10 ohm resistance in series having equivalent 30 ohm. which will be parallel with 10 ohm having equivalent resistance 15/2 ohm, ehich will be in series with two resistance of qo ohm. So equivalent resistance will be 55/2 = 27.5 ohm.