How do I calculate the net resistance in a complex resistor circuit?

[Spyder22]

I really confused by this circuit: http://myspace.homelinux.com:32123/circuit.jpg
When calculating the net resistance from A to C, how do I know if any current goes through 2 and 7? If there was current going through them, I have clue how they would contribute to the total circuit. For the second question, I don't even know where to start. Obviosly, the net resistance will be a little lower than just 1, but how the heck would you figure out the rest of it??

 

[Rohin.T.Narayan]

hello buddy ,
you please go and take your physics book and read wheatstones principle. In the given circuit since all resistances are having same value .there is no current in the segment connecting B&D.Now I think it will be eay for you,remove boxes
2 and 7.Using series ,parallel concepts you can solve the first part.(it is just R itself)

The second part is a bit tricky I'll tell it tomarrow

 

[Spyder22]

Thank you Rohin, I suspected there would be no current through those two resistors, but did not know how to prove it. I will have to read more on the internet about these wheatstone princeples as my book doesn't cover it. This makes the first problem very easy, but if you could provide some suggestions for the second that would be great!