I didnot understand the relation between speed and V.

I assume that you have difficulty in understanding the relation between speed of sound and frequency denoted by letter . (this letter is not 'V', it is a greek letter pronounced as 'nu'). This 'nu' represents frequency of sound. 

 

Wavelength : -The distance travelled by a wave in one time period of vibration of the particle of the medium is called the wavelength of the wave. It is denoted by ‘λ’. Its SI unit is metre (m).

 

We know, 

 

... (1) 

The number of oscillations made by the particle of the medium per unit time is called the frequency of the wave. It is denoted by ‘n’, ‘f’ or ‘’ 

 

Thus, 

 

 ... (2)   

 

From (1) and (2) 

 

We can say,