OG 12 Q213

[ss1]

In an electric circuit, two resistors with resistances x
and y are connected in parallel. In this case, if r is the
combined resistance of these two resistors, then the
reciprocal of r is equal to the sum of the reciprocals of
x and y. What is r in terms of x and y ?
(A) xy
(B) x + y
(C)1/(x + y)
(D)(Xy)/(x + y)
(E)(x + y)/(xy)

Cant the answer be x+y=r? OA: D

[sonikamadala]

yes. IMO is D.
Resistors are connected in parallel.

so 1/r = (1/x) + (1/y)

1/r = (x+y)/xy
r= xy/(x+y)


so D wins

[xperience]

Originally Posted by ss1

If r is the
combined resistance of these two resistors, then the
reciprocal of r is equal to the sum of the reciprocals of
x and y.
Cant the answer be x+y=r? OA: D

How can x + Y = r, when it is clearly mentioned "reciprocal"?