2 Answers

This is from a previous Yahoo answer:
You can find the wavelength of a sound wave of known frequency and velocity using the wave equation:
v = f x lambda
where
v = velocity (around 340 m/s for sound)
f = frequency (Hz)
lambda = wavelength (m)
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Since you know the frequency and wavelength you can multiply to get 410 * 0.8 = 328 meters/second

A wave with frequency of 410 Hz has 410 cycles each second. So the time of each of those cycles must be (1/410) seconds. How far did the wave travel in that time? 0.800 m.
How do you get velocity out of that?
v = distance / time = 0.800 m / (1/410) s = 328 m/s