DC circuitsQuestion 639 of 1506

Resistors of 100 Ω, 220 Ω and 470 Ω are connected in parallel. Which value is the best estimate of the total resistance?

  1. About 790 Ω
  2. About 60 Ω
  3. About 263 Ω
  4. About 100 Ω
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Correct answer: About 60 Ω

1/R = 1/100 + 1/220 + 1/470 = 0.0167 S, so R is about 60 Ω. It must be less than the smallest resistor.

Source: Lessons in Electric Circuits I: DC (Kuphaldt), 5.3: Simple Parallel Circuits

Practice dc circuits

Questions last reviewed: 18 October 2026