Step-by-step explanation:
Effective resistance in the 30Ω and 40Ω parallel circuit = 1 / (1/30 + 1/40) = 120/7 Ω.
20Ω + 10Ω = 30Ω
Effective resistance in the 50Ω and (20Ω + 10Ω) parallel circuit = 1 / (1/50 + 1/30) = 75/4 Ω.
Now we can add the resistances up:
Effective resistance for circuit
= 120/7 Ω + 75/4 Ω = 1005/28 Ω.
Hence I = V / R
= 9.0V / (1005/28 Ω) = 0.25A. (2s.f.)
