What is the equivalent resistance for a parallel circuit that has two resistors: 18.0 ohms and 23.5 ohms?

A.

10.2 ohms

B.

20.8 ohms

C.

5.5 ohms

D.

41.5 ohms

A

Explanation:

First of all the answer is less than the smallest resistor, so it is less than 18 ohms.

1 / r1 + 1 / r2 = 1/r

1/18 + 1/23.5 = 1/r

1/18 = 0.05555555

1/23.5 = 0.0422532

1/18 + 1/23.5 = 0.0555555 + 0.0422532

1/r = 0.0981087

r = 1/0.0981087

r = 10.193

A