In a parallel circuit with an 18 ohm and a 9 ohm resistor, what is the total resistance?

To find the total resistance in a parallel circuit, the formula used is:

1 / R_total = 1 / R1 + 1 / R2

Where R1 and R2 are the resistances of the individual resistors. In this case, we have an 18 ohm resistor and a 9 ohm resistor.

Applying the formula:

1 / R_total = 1 / 18 + 1 / 9

To simplify the right side:

1 / 9 can be rewritten as 2 / 18, so:

1 / R_total = 1 / 18 + 2 / 18 = 3 / 18

Now, taking the reciprocal gives:

R_total = 18 / 3 = 6 ohms

This shows that the total resistance in the circuit is indeed 6 ohms. Therefore, the answer is correct based on the calculations for total resistance in a parallel configuration.