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# What is the value of the third resistor?

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## What is the value of the third resistor?

A three-branch parallel circuit has a total resistance of 385.83 ohms. Two of the resistors are 680 ohms and 1500 ohms. What is the value of the third resistor?
Why is this wrong

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Originally Posted by samfulton
A three-branch parallel circuit has a total resistance of 385.83 ohms. Two of the resistors are 680 ohms and 1500 ohms. What is the value of the third resistor?
Why is this wrong
Let x = third resistor
1/R1 + 1/R2 + 1/R3 = 1/Rtotal
Rearrange the equation
1/Rtotal - 1/R1 - 1/R2 = 1/R3
1/358.83 - 1/680 - 1/1500 = 1/x
When solved x = 2200 ohm

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Originally Posted by kwegley
Let x = third resistor
1/R1 + 1/R2 + 1/R3 = 1/Rtotal
Rearrange the equation
1/Rtotal - 1/R1 - 1/R2 = 1/R3
1/358.83 - 1/680 - 1/1500 = 1/x
When solved x = 2200 ohm
I believe this is incorrect, can you actually demonstrate your calculations!