[tex]v = f \times λ \: [/tex]
V = Speed
f = frequency of wave
λ = no of wavelengths
Note that in a string, the number of wavelengths is given by;
[tex] \frac{λ}{2} = l \\ \\ λ = 2l[/tex]
l is the length of the string
Hence, λ = 2 × 0.9 = 1.8
Substitute the value of λ in the first equation ;
[tex]v = f \times λ \\ \\ v = 256 \times 1.8 = 460.8m {s}^{ - 2} [/tex]
