(20 10? 6? Changchun (1) is shown in figure 1. Three containers with the same volume, A, B and C, are connected by valves. From a certain moment, open the valve of container A.

Solution: (1) When t=3, A fills container B with water for 3 minutes.

Yb = 50+4t = 50+4×3 = 62；

(2) Solving in two stages, when 0≤t≤5, Yb = 50+4t;

When 5 < t ≤ 10, Yb = 50+4× 5-10 (t-5) =120-10t,

The functional relationship between Yb and t is Yb = 50+4t (0 ≤ t ≤ 5) Yb =120-10t (5 < t ≤10) (3) As can be seen from the image, Ya: Yb: YC = 2.

If 0≤t≤5, and t=5, yc=70, yb=3×704=50+4t, and ya = 35 < 40 does not conform to the ya image;

If 5 < t ≤ 10 and t= 10, then ya=40, yb= 120- 10t, yc= 10t+20, and the control image conforms to the function image.

Solution: t = 6.