Last Physics problem for this set, please help!?

Question

The mass of a string is 3.30 10-3 kg, and it is stretched so the tension in it is 110 N. A transverse wave traveling on this string has a frequency of 260 Hz and a wavelength of 0.60 m. What is the length of the string?

Answer 1

I hope it is vibrating at its fundamental frequency :-)

f=v/2L ; v=2fL
v=sqrt(T/(m/L)

or

2fL= sqrt(L T/m)
4f^2 L^2 = L T /m
L= T/(4m f^2)
L=110 /(4 x 3.30 E-3 260^2)
L=0.123 m