Question

Answerer of question (b) in the above picture please answer it fast...

Answer 1

1/Rp = 1/2+1/2 = 2/2 = 1.
Rp = 1.
Rs = 1 + 4 = 5 ohm.

Answer 2

The resistances ab and bc are connected in series. So the effective resistance in branch a-b-c becomes:-
2 +2=4ohms.
Now this effective resistance 4 ohms is in parallel with resistance ac=4 ohms. Hence the effective resistance will be:- $\frac {1}{R_{eff}}= \frac {1}{4} + \frac {1}{4} \\ =\frac {2}{4}\\ =\frac {1} {2}\\ \implies R_{eff}=2\ohms$
So the resistance between A and B is 2 ohm.