Calculations in hours and minutes become faster and without errors: add, subtract, multiply or divide hours and minutes is remarkably simple. In everyday life, we speak in minutes. But to facilitate the calculations, official documents often do not use the "minutes" but "decimal of an hour." 60 minutes = 1 hour = 100 hundredths.
Now you can make any opération in hrs:mins or hrs.decimal. You can at any time convert hrs:mins to hrs.decimal or vice versa.