A guitar string produces 3 beats/s when sounded with a 350-Hz tuning fork and 8 beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency of the string? Explain your reasoning.

347 Hz

Explanation:

Let the vibrational frequency be f.

so, f = 350 + 3 or 350 - 3 = 353 Hz or 347 Hz

And

f = 355 + 8 or 355 - 8 = 363 Hz or 347 Hz

So, 347 is common in both the cases,

Thus, the vibrational frequency is 347 Hz.