Réponse:

a) 25min 12s 1min=60s

25×60=1500+12=1512s

valeur decimale 0,42

1512÷3600(1h=3600s) 1h=60min

b) 5h39min36s

5h=18000s (5×3600)

39min= 2340s (39×60)

18000+2340+36=20376

valeur decimale 20376÷3600=5,66

c) 3h08min24s

3×3600=10800s

8min=480s

10800+480+24=11304s

valeur decimale 11304÷3600=3,14

d) 6h33min54s

6×3600=21600s

33min= 1980

21600+1980+54=23634s

valeur decimale 23634÷3600=6,565