Answer:
Time period between the successive beats will be 0.1703 sec
Step-by-step explanation:
We have given speed of the sound v = 349 m/sec
Wavelength of piano

Wavelength of piano

So frequency of piano A

Frequency of piano B

So beat frequency f = 455.61 - 449.74 = 5.87 Hz
So time period

So time period between the successive beats will be 0.1703 sec