What is the deviation ratio of an FM phone signal having a maximum frequency swing of plus or minus 7.5 kHz if the highest modulation frequency is 3.5 kHz?

Explication

Divide the maximum swing by the highest modulating frequency: 7.5 kHz ÷ 3.5 kHz ≈ 2.14. Answers around 0.21 come from inverting the fraction or from misplacing the decimal point.