Question

You are given five identical resistors each of resistance r. How can you arrange all these resistors (in series, in parallel, or both) in order to have an equivalent resistance of 7r/2, 7r/3 or 2r

Answer 1

r/2 + 3r = r/2 + 6r/2 = 7r/2 = 2 in parallel and 3 in series.

r/3 + 2r = r/3 + 6r/3 = 7r/3 = 3 in parallel and 2 in series.

Answer 2

r/2 + r/2 + r = 2r = 2 in parallel + 2 in parallel + 1 in series.