What is the resonant frequency of a parallel RLC circuit if R is 4.7 kilohms, L is 2 microhenrys and C is 30 picofarads?

To find the resonant frequency, you must use the standard formula: f = 1 / (2π√(LC)). Notice that the 4.7 kilohm resistor is extra information; while resistance changes the bandwidth of a parallel RLC circuit, it is ignored when calculating the ideal resonant frequency for these exam problems. Convert the given values to standard units: L is 2 × 10^-6 H, and C is 30 × 10^-12 F. Multiplying them together yields an LC product of 60 × 10^-18. The square root of this product is approximately 7.746 × 10^-9. Multiplying by 2π gives about 48.67 × 10^-9. Dividing 1 by this value results in approximately 20,540,000 Hz, or 20.5 MHz. Choosing the kHz option is a classic error stemming from incorrect scientific notation management.