Cannot find V and I in this circuit

[alacey11]

Homework Statement

Obtain the values of i and v in the circuit below:
http://img33.imageshack.us/img33/7538/newpicturenl.png
Answers: i = 6 Amps, v = 3 Volts

Homework Equations

Ohm's Law, Kirchhoff's Current Law & Kirchhoff's Voltage Law

The Attempt at a Solution

I have spent the last 90 minutes on this question!
I can see that it is simple, but I must be approaching it wrong as I keep on getting the same wrong answers.
I just need to know where to start...
Thanks

 

[doublea500]

id try combining the furthest resistances to the right because it is a series circuit, to get 9S then finding the total resistance of that and 2S which is 1/9S+1/2S=1/Rt ->2/18+9/18->11/18->18S/11= Rt. then find the total resistance of that and4s because its a series circuit. so its 18S/11 + 4S which is 62S/11... not sure if this is correct/and if it is idk where to go from there

 

[alacey11]

You approached it the same way I did :)
I thought that way would work, but I kept ending up with i = 1.35 A

 

[doublea500]

hmm, couldn't you do it that way then "simplify" it to a series circuit so I is constant. then can't you do V=IR and plug in 9 for Itotal and whatever the total resistance was for R and find V total? only problem here is S though.

 

[gneill]

The S unit is Siemens, which is conductance, not resistance. For an individual resistor, S = 1/R. This means that conductances in parallel add, while those in series add like resistances in parallel.

Sometimes it's easier just to convert all of the individual conductances to resistances...

 

[alacey11]

I had no idea they were different units!
I thought the S was a variable...

Thank you for clearing that up for me - I've solved the question now, thanks.