What is the Current and Power in the Circuit?

[happytailsgal]

Homework Statement

For the circuit in the figure, what is the current through the 2.0 ohm resistor?
Express your answer using two significant figures.

For the circuit in the figure, what is the power dissipated by the 20 ohm resistor?
Express your answer using two significant figures.

Homework Equations

V=IR for the first one and I'm not sure for the second.

The Attempt at a Solution

I thought it would be 100/(1/5 + 1/5)inverse + (1/2+1/4) inverse but its wrong. And I am not sure about the second./

 

[songoku]

Hi happytailsgal

First, you have to find the total resistance of the circuit then use the equation you wrote to find the current. For the second one, use the formula P = I²R

 

[happytailsgal]

Ok well that's where I'm having trouble at. How do I know which ones to add first for the resistors? What I mean is, do I add all the parallel first or all the series or does it not matter? The way I'm doing it now isn't yieldingthe right answer

 

[songoku]

Start from the furthest resistors from the source