The distance between two succesive crests of a wave corresponds to its wavelength, therefore the wavelength of this wave is
[tex]\lambda=1.20 m[/tex]
The frequency of a wave is the number of crests that passes through a given point in a certain time; therefore, for this wave it is:
[tex]f= \frac{N}{t}= \frac{8}{13.00 s}=0.62 Hz [/tex]
And now we can calculate the wave speed, which is given by the product between the wavelength and the frequency:
[tex]v= \lambda f = (1.20 m)(0.62 Hz)=0.74 m/s[/tex]
