Question

Three resistances of 12 , 16 , and 20 are connected in parallel. What resistance must be connected in series with this combinations to give a total resistance of 25 ?

Answer 1

Total resistance in parallel is Rp

So (1/Rp) = (1/12)+(1/16)+(1/20)

Rp = ?

impedance is 25

25 = Rp + Rs

put the value of Rp you'll get the answer.