One day is 24 hours.
Since there are 60 minutes in one hour there are 1440 minutes in one day.
5 hours 20 minutes is the same as 300+20, 320 minutes.
So 5hr 20min is [tex]\frac{320}{1440}[/tex] of the day.
(we can simplify that to [tex]\frac{2}{9}[/tex])
:)