Sound at air in STP travels at 343 m/s.
We also know the formula v=f lambda where v is the velocity, f is the frequency and lambda is the wavelength.
Substituting in values to this, we get:
343 = 256 * lambda
lambda = 343/256
=1.34 3sf
Aaand upon doing this, I realise your textbook wants you to assume the speed of sound to be 330m/s, right then, well changing the value to 330, we get 1.29m
