how did you get R4 in this question
Hi Leon, for this one you use current splitting and Ohm's Law.
The total current through R4 and R5 is 9 A.
R5 has 5 A flow through it, and is 36 Ω.
The voltage across R5 (and R4) is therefore 180 V.
The question then becomes, "what is the value of R4 such that it has a voltage drop of 180 V when the current is 4 A?"
Thanks
Bart
thanks