The wavelength of the note is 
. Since the speed of the wave is the speed of sound, 
, the frequency of the note is
Then, we know that the frequency of a vibrating string is related to the tension T of the string and its length L by
where
is the linear mass density of our string.
Using the value of the tension, T=160 N, and the frequency we just found, we can calculate the length of the string, L:
Then, we know that the frequency of a vibrating string is related to the tension T of the string and its length L by
where
Using the value of the tension, T=160 N, and the frequency we just found, we can calculate the length of the string, L: