12 = 2²x3
15=3x5
cmmmc=2²x3x5=60
1 robinet poate umple in 60 ore 60:12 =5 bazine
al 2-lea robinet poate umple in 60 ore 60:15 =4 bazine
daca sunt descise simultan vor umple in 60 ore 5+4=9 bazine
deci 1 bazin se va umple in
60:9=6,(6) ore = 6ore 40 min
1 ora = 60 min
0,(6) ore=6/9 x60= 40 min
