The relationship between the frequency f of a wave, its wavelength [tex]\lambda[/tex] and its speed v is given by
[tex]v=\lambda f[/tex]
The wave of our exercise has a speed of [tex]v=250 m/s[/tex] and a wavelength of [tex]\lambda=3.5 m[/tex], so re-arranging the previous equation we can find its frequency:
[tex]f = \frac{v}{\lambda}= \frac{250 m/s}{3.5 m}=71.4 Hz [/tex]
