
$\therefore \frac{{R{R_2}}}{{R + {R_2}}} + {R_1} = R \Rightarrow 2R + R + 2 = {R^2} + 2R$
$ \Rightarrow {R^2} - R - 2 = 0 \Rightarrow R = - 1$ or $R = 2\,ohm$



$I.$ All the $10$ laptops can be powered by the $UPS$, if connected directly.
$II.$ All the $10$ laptops can be powered, if connected using an extension box with a $3 \,A$ fuse.
$III.$ If all the $10$ friends use the laptop for $5 \,h$, then the cost of the consumed electricity is about $₹ 22.50.$
Select the correct option with the true statements.