If a circuit has resistances of 5, 10, and 20 ohms connected in parallel, what is the combined total resistance of the circuit?

Correct Answer: Option B — 2.9 ohms

Parallel resistance formula 1/Rt = 1/R1 + 1/R2 + 1/R3 yields 1/5 + 1/10 + 1/20 = 0.2 + 0.1 + 0.05 = 0.35 siemens. Taking the reciprocal 1/0.35 results in 2.857 ohms, rounding correctly to 2.9 ohms per standard IEEE 45 marine electrical calculation methods.