試題詳解

47. A tuning fork is known to vibrate with frequency 262 Hz. When it is sounded along with a mandolin string, four beats are heard every second. Next, a bit of tape is put onto each tine of the tuning fork, and the tuning fork now produces five beats per second with the same mandolin string. What is the frequency of the string?
(A) 257 Hz
(B) 258 Hz
(C) 262 Hz
(D) 266 Hz
(E) 268 Hz