The four Resistances P,Q,R and S of a wheat stone bridge are 4,10,20 and 200Ω respec-tively. To balance the brige

$\frac{\mathrm{P}}{\mathrm{Q}}=\frac{4}{10},\frac{\mathrm{R}}{\mathrm{S}}=\frac{20}{200}\therefore \frac{2}{5}=\frac{1}{10};\mathrm{R}$ is to be increase
or ‘S’ to be decrease. 
Which mean R+ series or S+ parallel
$\begin{array}{l}\frac{\mathrm{P}}{\mathrm{Q}}=\frac{\mathrm{R}}{\mathrm{S}};\frac{\mathrm{P}}{\mathrm{Q}}=\frac{\mathrm{R}}{\left(\frac{\mathrm{Sx}}{\mathrm{S}+\mathrm{x}}\right)}\\ \frac{4}{10}=\frac{20(200+\mathrm{x})}{200\mathrm{x}};\mathrm{x}=\frac{200}{3}\mathrm{\Omega }\end{array}$
$\therefore \frac{200}{3}$should be connected parallel to 200Ω