Salut !
3 h 15 mn = 3 h + (15/60) h = 3 h + (1/4) h = 3 h + 0,25 h = 3,25 h
5 h 24 mn = 5 h + (24/60) h = 5 h + (2/5) h = 5 h + 0,4 h = 5,4 h
