For all waves, wave speed (v, in metres per second, m/s) is found from frequency (f, in hertz, Hz) and wavelength (λ, in metres, m):
wave speed = frequency × wavelength, or v = f × λ
For example, a wave of frequency 50 Hz and wavelength 0.4 m has a speed of 50 × 0.4 = 20 m/s. Rearranged, wavelength = wave speed ÷ frequency, and frequency = wave speed ÷ wavelength. So a wave moving at 12 m/s with a frequency of 4 Hz has a wavelength of 12 ÷ 4 = 3 m.
Wave speed also equals distance divided by time: wave speed = distance ÷ time, or v = x ÷ t. Sound in air travels at about 340 m/s. Rearranged, time = distance ÷ wave speed, so a wave at 12 m/s takes 5 s to travel 60 m. Always use metres, seconds and hertz in the equations.