The wavelength of a sound wave from a tuning fork is 0.85m. What is the frequency of the tuning fork? If the velocity of sound in air $=340{ \mathrm{ms}}^{-1}$

We know that, 

speed $\left(v\right)=$ wavelength $\left(\lambda \right)\times$ frequency (f).
 Given,
The wavelength $\left(\lambda \right)$of the tuning fork $=0.75 \mathrm{m}$
We need to find Frequency (f)=?
Speed $\left(v\right)=f\times \lambda =340 \mathrm{m}/\mathrm{s}$
$\Rightarrow f=\frac{340}{0.75}=453 \mathrm{Hz}$