Figuring this circuit out. HELP

[Skynt]

Okay I have to show that between points a and b the resistance (ab) is equal to 27/17 ohms.

Here's the diagram:

http://img231.imageshack.us/img231/4614/testln9.jpg

The hint was given to determine the emf/I where I is the current through the battery.
I've found different ways of getting 27/17 out of it but I need to be able to explain why.

 

[John Creighto]

It's not obvious to me on how to combine the resistances so I'd use loop or nodal analysis.

 

[Skynt]

How?

 

[Skynt]

I forgot to mention that the EMF is connected across points a and b

 

[John Creighto]

I'm sure this is all in your text but:

Loop Analysis
http://mathonweb.com/help/backgd4.htm

Nodal Analysis
http://mathonweb.com/help/backgd5.htm

Y Delta Transformation
http://en.wikipedia.org/wiki/Y-Δ_transform

If you use the Y Delta method remember how resisters add based if they are in series or parallel. If you use either loop or nodal analysis then add up the current going out of node a or into node b. You'll do the same thing if you use loop analysis but you'll have to convert from current to voltage via ohms law.