Two wavelengths, find time between successive beats

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phys62
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Two pianos each sound the same note simultaneously, but they are both out of tune. On a day when the speed of sound is 348 m/s, piano A produces a wavelength of 0.765 m, while piano B produces a wavelength of 0.772 m. How much time separates successive beats?


So I know:
v=348 m/s
wavelength of A=0.765 m
wavelength of B=0.772 m
f=v/wavelength

so I was able to find the frequency of A=454.9 and frequency of B=450.7
I'm just not really sure what I should be doing... seems like it should be just a one or two step problem.. :/
 
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OK what is the difference in frequency?

Isn't a beat going to be counted when ever their maxima coincide? So say the difference between 2 tones Δf is 1/2 hz, then won't the time T between maxima be 1/Δf = 2 ?
 
Yes, you're right! Thanks so much!