Question

Va rog frumos sa o rezolvati.Dau coroana.
Inatrun bazin curge apa prein doua robinete timp de cinci ore dupa care primul robinet se inchide,iar al doilea mai curege un timp de doua ore.In bazin s-au adunat 5000 L apa.Alta data primul robinet curge timp de trei ore,al doilea sase ore si in bazin se strange 3900 L.In cate ore umple bazinul al doilea robinet singur,daca primul robinet il umpe in 20 ore.

Answer 1

a=debitul robinet 1
b=debitul robinet 2
5a+(5+2)b=5000
5a+7b=5000
3a+6b=3900
a+2b=1300
a=1300-2b
5(1300-2b)+7b=5000
6500-10b+7b=5000
3b=1500
b=500 l/h
a=1300-2×500=300 l/h
Vbazin=500 l/h × 20 h=10000 l
10000 l :300=33,(3) = 30 h  20 min
0,(3)= 3/9=1/3 h
1/3 h × 60 min/h=20 min

Answer 2

a=debitul robinet 1 b=debitul robinet 2 5a+(5+2)b=5000 5a+7b=5000 3a+6b=3900 a+2b=1300 a=1300-2b 5(1300-2b)+7b=5000 6500-10b+7b=5000 3b=1500 b=500 l/h a=1300-2×500=300 l/h Vbazin=500 l/h × 20 h=10000 l 10000 l :300=33,(3) = 30 h 20 min 0,(3)= 3/9=1/3 h 1/3 h × 60 min/h=20 min