Question Detail
Question
20 kΩ resistor in series with 40 kΩ. What R in parallel with equivalent gives 20 kΩ?
Correct Answer
Option B is the correct answer.
Detailed Explanation
Series equivalent = 20+40=60 kΩ. Parallel: 1/20 = 1/60 + 1/R → 1/R = 1/20 – 1/60 = (3–1)/60 = 2/60 = 1/30 → R = 30 kΩ. Wait, that gives 30, not 120. Let me recalc: Target total = 20. 1/20 = 1/60 + 1/R → 1/R = 0.05 – 0.01667 = 0.03333 → R=30 kΩ. Option B. Yes, B.
Hint
Parallel combination formula.