PSLE The figure shows taps A and B and an empty tank. At 4 p.m., tap A was turned on. Water flowed into the tank from tap A at a rate of 2.7 litres per minute. After 8 minutes, tap B was turned on. At 4.10 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 4.30 p.m., what fraction of the tank was filled with water?
(a)
Volume of the tank
= 60 x 35 x 20
= 42000 mℓ
= 42 ℓ
Volume of the tank at 4.10 p.m. when it was half filled with water
= 42 ÷ 2
= 21 ℓ
Volume of water by Tap A for 8 min
= 8 x 2.7
= 21.6 ℓ
Duration that Tap B was turned
= 10 - 8
= 2 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 2 min
= 21.6 - 21
= 0.6 ℓ
Volume of water that flowed out in 1 min
= 0.6 ÷ 2
= 0.3 ℓ
Volume of water that flowed out of Tap B in 1 min
= 2.7 + 0.3
= 3 ℓ
(b)
Duration from 4.10 p.m. to 4.30 p.m. = 20 min
Volume of water that flowed out from 4.10 p.m. to 4.30 p.m.
= 20 x 0.3
= 6 ℓ
Volume of water left at 4.30 p.m.
= 21 - 6
= 15 ℓ
Fraction of the tank filled with water at 4.30 p.m.
=
1542 =
514
Answer(s): (a) 3 ℓ; (b) 514