# A schematic diagram includes both a parallel and a series circuit. R1 and R2 are parallel with R3. But R4 is in a series with R1. I know the... total resistance for the parallel circuit and the total resistance for the series circuit. How would I go about adding them to find the total resistance? Would I just simply add them? I am just confused because R1 is included in both the parallel circuit and the series circuit. Sorry if this is confusing. I have a test tomorrow and need to know how to do this. Thanks! First, R1 and R4 are in series with each other, suppose these two form an equivalent resistor R5, then,

R5 = R1+R4

Now this R5, R3 and R3 are in parellel to each other. Suppose these three form a equivalent resistor of R, then,

(1/R) = (1/R5) +(1/R2)+(1/R3)

(1/R) =...

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First, R1 and R4 are in series with each other, suppose these two form an equivalent resistor R5, then,

R5 = R1+R4

Now this R5, R3 and R3 are in parellel to each other.
Suppose these three form a equivalent resistor of R, then,

(1/R) = (1/R5) +(1/R2)+(1/R3)

(1/R) = (1/(R1+R4))+(1/R2)+(1/R3)

Multiply, Right hand side of the equation by ((R1+R4)R2R3)/((R1+R4)R2R3)

(1/R) = (R2R3+R3(R1+R4)+R2(R1+R4))/(R2R3(R1+R4))

By taking the reciprocal,

R = (R2R3(R1+R4))/(R2R3+R3(R1+R4)+R2(R1+R4))

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