PSLE The figure shows taps A and B and an empty tank. At 8 p.m., tap A was turned on. Water flowed into the tank from tap A at a rate of 3.3 litres per minute. After 7 minutes, tap B was turned on. At 8.13 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 8.22 p.m., what fraction of the tank was filled with water?
(a)
Volume of the tank
= 60 x 30 x 25
= 45000 mℓ
= 45 ℓ
Volume of the tank at 8.13 p.m. when it was half filled with water
= 45 ÷ 2
= 22.5 ℓ
Volume of water by Tap A for 7 min
= 7 x 3.3
= 23.1 ℓ
Duration that Tap B was turned
= 13 - 7
= 6 min
Since there was a decrease in the volume of water in the tank, water flowed out of Tap B at a faster rate than that of Tap A.
Volume of water that flowed out in 6 min
= 23.1 - 22.5
= 0.6 ℓ
Volume of water that flowed out in 1 min
= 0.6 ÷ 6
= 0.1 ℓ
Volume of water that flowed out of Tap B in 1 min
= 3.3 + 0.1
= 3.4 ℓ
(b)
Duration from 8.13 p.m. to 8.22 p.m. = 9 min
Volume of water that flowed out from 8.13 p.m. to 8.22 p.m.
= 9 x 0.1
= 0.9 ℓ
Volume of water left at 8.22 p.m.
= 22.5 - 0.9
= 21.6 ℓ
Fraction of the tank filled with water at 8.22 p.m.
=
21.645 =
1225
Answer(s): (a) 3.4 ℓ; (b) 1225