Two resistors R₁ = (4 $\pm$ 0.8) $\Omega$ and R₂ = (4 $\pm$ 0.4) $\Omega$ are connected in parallel. The equivalent resistance of their parallel combination will be :

Given, <br/><br/>R₁ = (4 $\pm$ 0.8) $\Omega$<br/><br/>R₂ = (4 $\pm$ 0.4) $\Omega$<br/><br/>Equivalent resistance when the resistors are connected in parallel is given by<br/><br/>$${1 \over {{R_{eq}}}} = {1 \over {{R_1}}} + {1 \over {{R_2}}} \Rightarrow {1 \over {{R_{eq}}}} = {1 \over 4} + {1 \over 4}$$<br/><br/>${R_{eq}} = 2\,\Omega$<br/><br/>Now, $${{\Delta {R_{eq}}} \over {R_{eq}^2}} = {{\Delta {R_1}} \over {R_1^2}} + {{\Delta {R_2}} \over {R_2^2}}$$<br/><br/>Substituting the values in the above equation, we get<br/><br/>$${{\Delta {R_{eq}}} \over 4} = {{0.8} \over {16}} + {{0.4} \over {16}} \Rightarrow \Delta {R_{eq}} = 0.3\,\Omega $$<br/><br/>$\therefore$ The equivalent resistance in parallel combination is ${R_{eq}} = (2 \pm 0.3)\Omega$.