Sound waves consists of $20$ compressions and $20$ rarefactions in $10\text{m}$ length. The wavelength of the waves is

In a longitudinal sound wave, one complete wave cycle (one wavelength, $\lambda$) consists of one compression paired with one adjacent rarefaction.Given:The wave train contains $20$ compressions and $20$ rarefactions, which means there are exactly $N=20$ complete wave cycles.The total span length ($L$) occupied by these waves is $10\text{m}$.The formula relating total length to wavelength is:
$$L=N\cdot \lambda$$
$$10\text{m}=20\cdot \lambda ⟹\lambda =\frac{10}{20}=0.5\text{m}$$
Converting meters into centimeters:
$$\lambda =0.5\times 100\text{cm}=50\text{cm}$$