In Young's double slit experiment, the ${10}^{\text{th}}$ maximum of wavelength ${\mathrm{\lambda }}_1$ is at a distance of ${\mathrm{y}}_1$ from the central maximum. When the wavelength of the source is changed to ${\mathrm{\lambda }}_2$, 5^th maximum is at a distance of ${\mathrm{y}}_2$ from its central maximum. The ratio $\genfrac{}{}{0.1ex}{}{{\mathrm{y}}_1}{{\mathrm{y}}_2}$ is