A $900 \mathrm{~mm}$ internal diameter sewer is laid at a slope of $0.004$ and has an actual flow of $0.15 \mathrm{~m}^3 / \mathrm{s}$. Assuming Manning's roughness coefficient to be $0.013$, the ratio of the actual flow to the flow when the sewer is running full is__________. $\text{(rounded off to two decimal places)}$.
Take $\pi=3.14$.
