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## Homework Statement

Given: The power absorbed by the 15 ohm resistor is 15 W. Find R.

http://sphotos-a.xx.fbcdn.net/hphotos-snc7/384382_495043340515186_1992745410_n.jpg [Broken]

## Homework Equations

parallel circuit for 2 resistor: R

_{eq}=R

_{1}R

_{2}/ R

_{1}+R

_{2}

Voltage Division Rule: for series circuit V

_{R2}= V

_{s}R

_{2}/(R

_{1}+R

_{2})

## The Attempt at a Solution

P = V

^{2}/R

P = 15W, R = 15Ω

P at 15Ω = 15 W => V at 15Ω = 15V

=> V at R = 25V - 15V = 10V

So I go around the circuit from the left to right.

Start at the double 4Ω => R

_{eq}= 2Ω

the 2Ω + 6Ω || 24Ω => R

_{eq}= 6Ω

6Ω+4Ω || 15Ω => R

_{eq}= 6Ω

now the circuit only have R and the 6Ω

apply V

_{R2}= V

_{s}R

_{2}/(R

_{1}+R

_{2})

Plug in the number

solve for R = 4Ω

Please let me know if this is the right approach or if I have made a mistake.

Thanks for your time.

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