The speed of sound at 0°C is approximately v=331.2 m/s. The frequency of the sound wave is f=990 Hz. To find the wavelength of the wave, we can use the basic relationship between frequency, wavelength and speed of a wave:
[tex]\lambda= \frac{v}{f} [/tex]
where [tex]\lambda[/tex] is the wavelength. If we use the data of the problem, we find
[tex]\lambda= \frac{331.2 m/s}{990 Hz} =0.33 m[/tex]