What is the maximum resistance which can be made using five resistors each of 1/5 Ω?
(a) 1/5 Ω
(b) 10 Ω
(c) 5 Ω
(d) 1 Ω

Solution: The answer is (d) 1 Ω

Resistance is maximized by connecting resistors in series.
$$
\begin{aligned}
& R =\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5} \
&=5 / 5 \
&=1 \Omega
\end{aligned}
$$