Water flows into a container through Tap R and flows out of the container through Tap S. The capacity of a container is 42 litres. When only Tap R is turned on, the container is completely filled in 12 minutes. When only Tap S 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 42% of the container?
- How much water has flowed out through Tap S by the time the container is 25 filled with water? Express your answer in litres.
(a)
Tap R :
12 min → 1 container
1 min →
112 container
12 hour =
12 x 60 = 30 min
Tap S:
30 min → 1 container
1 min →
130 container
Tap R and Tap S:
1 min →
112 -
130 =
560 -
260 =
120 container
1 container →
201 = 20 min
42% container → 42% x 20 = 8.4 min
(b)
Time taken to fill
25 of the container
1 container → 20 min
25 container → 20 x
25 = 8 min
Volume that flows out per min
=
130 container
=
130 x 42
= 1.4 ℓ
Volume of water that flowed out through Tap S in 8 min
= 8 x 1.4
= 11.2 ℓ
Answer(s): (a) 8.4 min; (b) 11.2 ℓ