Node Voltage Method: Solve for v0 in Circuit

[orangeincup]

Homework Statement

Use the node-voltage method to find v0 in the circuit below.

Homework Equations

i1+i2+...in=0
i=v/R

The Attempt at a Solution

So I set my reference node to the top of the middle line(above 25Ω)
Equation...
24V/(20+80)Ω+v0/25+.004A=0

Now I can solve for v0=(-.004-24/100 )* 25, v0=-6.1V

I think I did something wrong, I'm confused about a few things. How do I know where to take my reference node? Also, I'm solving for v0, yet I'm adding .004 amps to the answer. Since I'm solving for voltage, how is this possible?

Edited:Uploaded picture

 

[ehild]

I do not see any figure.

ehild

 

[ehild]

Homework Statement

Use the node-voltage method to find v0 in the circuit below.

Homework Equations

i1+i2+...in=0
i=v/R

The Attempt at a Solution

So I set my reference node to the top of the middle line(above 25Ω)
Equation...
24V/(20+80)Ω+v0/25+.004A=0

that is not correct. The current through the 20+80Ω resistors flows through the potential difference v0-24V.

ehild

 

[orangeincup]

Oh I see. I updated my solution:

(v0-24)/100+v0/25+0.004A=0

v0/100Ω+v0/25Ω=24V/100Ω-0.004A

0.05v0=.24A-.004A

v0=4.72V

 

[ehild]

Oh I see. I updated my solution:

(v0-24)/100+v0/25+0.004A=0

It is much better, but 40 mA=0.04 A.

ehild

 

[orangeincup]

Okay, I fixed it. v0=4.00V. Thank you.