The total resistance measured at PQ in the diagram above is

Explanation

The three 2 ohms are in series, therefore the total resistance is
\(R=R_1+R_2+R_3\)
\(R_ {total} =2+2+2= 6\) ohms.

resketching circuit;
6 ohms is used to replace the three 2 ohms which is therefore placed by the 3 ohms resistor.
The 3 ohms and 6 ohms resistors are in parallel, so the combined resistance is
\(R=\frac{R_1xR_2}{R_1+R_2}\)
\(R= \frac{3×6}{3+6}\)
\(R=\frac{18}{9}=2\) ohms.
Resketching circuit:
The 2 ohms is used to replace the 3 ohms and 6 ohms laying side-by-side.
Therefore, the 3 resistors (1 ohm, 1 ohm, and 2 ohms) are in series.
Thus, the total resistance is
\(R= (R_1+R_2+R_3)\)
\(R_{total} =1+1+2=4\) ohms.
Therefore, the total resistance measured at PQ is 4 ohms.