Given the value of Rydberg constant is ${10}^7{m}^{-1},$ the wave number of the last line of the Balmer series in hydrogen spectrum will be

$\text{ Here, }R={10}^7{ \mathrm{m}}^{-1}$

The wave number of the last line of the Balmer series in hydrogen spectrum is given by

$\frac{1}{\lambda }=R\left(\frac{1}{2^2}-\frac{1}{{\infty }^2}\right)=\frac{R}{4}=\frac{{10}^7}{4}=0.25\times {10}^7{ \mathrm{m}}^{-1}$