What mathematical operation is used to find the resistance of the heat strip at 230V rated power?

To find the resistance of a device when its rated voltage and power are known, you can use the formula derived from Ohm's Law and the power formula. The relationship between voltage (V), power (P), and resistance (R) can be expressed as P = V² / R. Rearranging this formula to solve for resistance gives us R = V² / P.

In the context of the question, at a rated voltage of 230V, you would square that voltage and then divide by the rated power to calculate the resistance. This matches precisely with the operation of taking the voltage squared and dividing by the power, confirming that this option is indeed the correct choice.

The other choices do not apply as directly to finding resistance in this scenario. Multiplication of voltage by current is related to power calculation but not resistance. Addition of resistances is relevant when combining resistors in a circuit, and taking the square root of power does not provide meaningful information in the context of this specific problem.