How Do You Calculate the Equivalent Resistance in This Circuit?

[rootX]

Homework Statement

Find equivalent resistance in:
http://img135.imageshack.us/img135/585/62083770ay3.jpg

Homework Equations

The Attempt at a Solution

my
r_eq^-1 = (30+60)^-1+(40+10)^-1
this is wrong.
do i need to include 8 and 4 ohm resistors

 

[stewartcs]

Homework Statement

Find equivalent resistance in:
http://img135.imageshack.us/img135/585/62083770ay3.jpg

Homework Equations

The Attempt at a Solution

my
r_eq^-1 = (30+60)^-1+(40+10)^-1
this is wrong.
do i need to include 8 and 4 ohm resistors

Based on your drawing your equation looks correct. What answer did you get?

You can check your answer against this equation's results:

$$R_{eq} = \frac{R_1 \cdot R_2}{R_1 + R_2}$$

R1 would be 90 since 30 and 60 are in series and R2 would be 50 for the same reason.

CS