Two-out-of-tune flutes play the same note. One produces a tone that has a frequency of 260 Hz, while the other produces 266 Hz. When a tuning fork is sounded together with the 260 Hz tone, a beat frequency of 1 Hz is produced. When the same tuning fork is sounded together with the 266 Hz tone, a beat frequency of 5 Hz is produced. What is the frequency of the tuning fork? I have no idea where to start. I know that Fbeat= f-Ffork, but I don't think that helps me any. Any ideas?