Water flows into a tank through Tap N and flows out of the container through Tap P. The capacity of a tank is 54 litres. When only Tap N is turned on, the container is completely filled in 12 minutes. When only Tap P 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 80% of the tank?
- How much water has flowed out through Tap P by the time the tank is 25 filled with water? Express your answer in litres.
(a)
Tap N :
12 min → 1 tank
1 min →
112 tank
12 hour =
12 x 60 = 30 min
Tap P:
30 min → 1 tank
1 min →
130 tank
Tap N and Tap P:
1 min →
112 -
130 =
560 -
260 =
120 tank
1 tank →
201 = 20 min
80% tank → 80% x 20 = 16 min
(b)
Time taken to fill
25 of the tank
1 tank → 20 min
25 tank → 20 x
25 = 8 min
Volume that flows out per min
=
130 tank
=
130 x 54
= 1.8 ℓ
Volume of water that flowed out through Tap P in 8 min
= 8 x 1.8
= 14.4 ℓ
Answer(s): (a) 16 min; (b) 14.4 ℓ