Answer:
The wavelength of the waves on the string is found using v = λf:
λ = v/f = 315/370 = 0.85135m
The first harmonic (fundamental) standing wave formed on the string has nodes only at the ends (see diagram in link) so:
String length = λ/2 = 0.85135/2 = 0.426m (to 3 sig. figs.)
