Question

Make r the subject and find the value​

Answer 1

`~~~~~~~~(1)/(R) = (1)/(R_1) + \frac 1{R_2}\\\\\\\implies \frac 1{R_2} = (1)/(R ) - \frac 1{R_1}\\\\\\\implies \frac 1{R_2} = (R_1 -R)/(RR_1)\\\\\\\implies R_2 = (RR_1)/(R_1-R)\\\\\\\text{When}~ R= 24~ \Omega ~ \text{and}~ R_1 = 30~ \Omega,\\\\R_2 = (24 * 30)/(30-24)~\Omega\\\\\\~~~~~=(720)/(6)~ \Omega\\\\\\~~~~= 120~ \Omega`