Water flows into a tank through Tap C and flows out of the container through Tap D. The capacity of a tank is 78 litres. When only Tap C is turned on, the container is completely filled in 12 minutes. When only Tap D is turned on, it takes
12 hour for all the water to flow out. If both taps are turned on at the same time,
- How long does it take to fill 86% of the tank?
- How much water has flowed out through Tap D by the time the tank is 45 filled with water? Express your answer in litres.
(a)
Tap C :
12 min → 1 tank
1 min →
112 tank
12 hour =
12 x 60 = 30 min
Tap D:
30 min → 1 tank
1 min →
130 tank
Tap C and Tap D:
1 min →
112 -
130 =
560 -
260 =
120 tank
1 tank →
201 = 20 min
86% tank → 86% x 20 = 17.2 min
(b)
Time taken to fill
45 of the tank
1 tank → 20 min
45 tank → 20 x
45 = 16 min
Volume that flows out per min
=
130 tank
=
130 x 78
= 2.6 ℓ
Volume of water that flowed out through Tap D in 16 min
= 16 x 2.6
= 41.6 ℓ
Answer(s): (a) 17.2 min; (b) 41.6 ℓ