1.  speed = frequency x wavelength       2.  speed = frequency ÷ wavelength      False            wavelength = speed ÷ frequency      Correct            frequency = speed ÷ wavelength      Correct            speed = wavelength ÷ frequency      False       3.  speed = frequency x wavelength            speed = 20 x 16.5            speed = 330 m/s       4.  Higher tier only:            frequency = speed ÷ wavelength            frequency = 300 000 000 ÷ 1500 000            frequency = 200 Hz