Final answer:
The frequency at which a 705 mm string will vibrate is approximately 342 cycles per second.
Step-by-step explanation:
When under equal tension, the frequency (f) of a vibrating string in a piano varies inversely with the string length. This means that as the string length increases, the frequency decreases, and vice versa.
To find the frequency at which a 705 mm string will vibrate, we can set up a proportion using the given values:
Frequency1 / Length1 = Frequency2 / Length2
Substituting the values into the proportion, we get:
515 cycles per second / 410 mm = Frequency2 / 705 mm
Solving for Frequency2, we find that it is approximately 342 cycles per second.