That's great for all of those EE's out there...oh wait, they're actually a small % of MBA seekers.

For the rest of us

reciprocal of x = 1/x

reciprocal of r = 1/r

reciprocal of y = 1/y

1/r = 1/x + 1/y

To get the same denominator

\(\frac{1}{r} = \frac{y}{y}*\frac{1}{x} + \frac{x}{x}*\frac{1}{y}\)

becomes

\(\frac{1}{r} = \frac{y}{xy} + \frac{x}{xy}\)

\(\frac{1}{r} = \frac{X + y}{xy}\)

Now you can get rid of the fraction with \(r\) by cross multiplying

r * (x+y) = 1*xy

and then dividing to get r alone

r = xy/x+y

fatb wrote:

droopy57 wrote:

The beginning of question is confusing...

two resistors with resistances x and y are connected in parallel. In this case, if r is the combined resistance of these two resistors

Does this have anything to do w/ the questions b/c to me, it seems the latter is purpose of question..

It just means r = value of (x//y)

Basically... this is EE101 of finding the equivalent resistor value.

1/r = 1/x + 1/y is the starting equation

1/r = (x+y)/xy

and r = xy/(x+y)

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J Allen Morris

**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

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