Q) What amateur band are you using if you are transmitting on 223.50 MHz?
A) 1.25 meter band
You can memorize this answer. Alternatively, you can learn and apply the underling theory which will help you beyond the test. The relationship between a radio signal's frequency and its wavelength is described by the following formula:
wavelength in meters = 300 / frequency in MHz
In the example above, wavelength = 1.34m = 300 / 223.50Mhz. On the test, the closest answer to the calculated wavelength is the 1.25m band.