Circuits Wired Partially in Series and Partially in Parallel

[StudentofPhysics]

R1 = 3 ohms; R2 = 6 ohms

What is the equivalent resistance between A & B?

I just can't find the right answer with this one.

I don't know if I'm placing the wrong ones in parallel. I've tried two different set ups. How exactly does this type of wiring set up work?




This one is giving me the same problem:
R1 = 3 ohms; R2 = 9 ohms ; R3 = 12 ohms
http://www.webassign.net/userimages/barrett.3@osu/CJ6-20-061-small.jpg

 

[chroot]

First, collapse the three series resistors on the right into a single resistor, (3 + 6 + R2) ohms. Next, combine that resistor in parallel with the 8 ohm resistor. Next, combine that in series with the 4 ohm resistor... etc.

- Warren

 

[Office_Shredder]

Break it up into a linear circuit:

10----------------------------B
A-R1-- | |
| 8-----| |
4------- |
6---R2----3---|

I apologize for it being so bootleg, but does this help?

EDIT: Apparently it collapsed all the empty space, so quote my post to see what it's really supposed to look like

 

[StudentofPhysics]

Warren,
Thanks for the help on the first circuit. I understand the technique now.

Not sure if I understand how to apply it to the 2nd but I'm trying right now.

 

[StudentofPhysics]

OS- thanks for the help but I got it.
The spacing was still messed up in the qoute though

Is it the same approach for the 2nd circuit?

 

[Office_Shredder]

For the second:

Combine R3 and the 9 ohm. Then that's in parallel with the 6 ohm. That, R1, and R2 are in series, and that's in parallel with the 20 ohm

 

[StudentofPhysics]

OK, I succeeded at # 2 aswell
thanks for allt he help

 

[Office_Shredder]

FOr future reference, even though you can't see my diagram very well, it's useful to take point b, and "rotate" it directly horizontal with point a. Then redraw the circuit, and what's in series and what's parallel should be more obvious