In hydrogen spectrum, the ratio of wavelengths of the last line of Lyman series and that of the last line of Balmer series is

The Rydberg formula for hydrogen spectral lines is given by $\frac{1}{\lambda} = R \left( \frac{1}{n_f^2} - \frac{1}{n_i^2} \right)$ where $R$ is the Rydberg constant, $n_f$ is the final quantum number, and $n_i$ is the initial quantum number.

For series limit transitions, $n_i = \infty$, simplifying the formula to $\frac{1}{\lambda} = \frac{R}{n_f^2}$.

The Lyman series limit corresponds to $n_f = 1$, giving $\lambda_L = \frac{1}{R}$.

The Balmer series limit corresponds to $n_f = 2$, giving $\lambda_B = \frac{4}{R}$.

The ratio of wavelengths is $\frac{\lambda_L}{\lambda_B} = \frac{\frac{1}{R}}{\frac{4}{R}} = \frac{1}{4} = 0.25$.

Final answer: $\boxed{0.25}$