Solving for Resistance in a Circuit

AI Thread Summary
The problem involves finding the unknown resistance R in a circuit with an equivalent resistance of 40 ohms between points A and B. The initial calculation incorrectly resulted in a negative value for R, indicating an algebraic error. A user suggests re-evaluating the calculations to correct the mistake. Proper application of circuit formulas is essential for accurate results. Reassessing the algebra should lead to the correct value of R.
whoopie88
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Circuit Resistance Problem!

Homework Statement


The equivalent resistance between points A and B of the resistors shown in the figure below is 40 . Find the value of resistance R.

21-30.gif


Homework Equations


All circuit formulas.

The Attempt at a Solution


40 - 12 = 28
28 = [(1/55) + (1/R)]^-1
R = -27

Help!
 

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whoopie88:

Your equation for the unknown R is OK, but a mistake in your algebra has led you to find a negative solution. Retry your calculations carefully and see if you can't solve your equation properly.
 

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