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 2.7 litres per minute. After 8 minutes, tap B was turned on. At 8.14 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 8.21 p.m., what fraction of the tank was filled with water?
(a)
Volume of the tank
= 60 x 30 x 15
= 27000 mℓ
= 27 ℓ
Volume of the tank at 8.14 p.m. when it was half filled with water
= 27 ÷ 2
= 13.5 ℓ
Volume of water by Tap A for 8 min
= 8 x 2.7
= 21.6 ℓ
Duration that Tap B was turned
= 14 - 8
= 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
= 21.6 - 13.5
= 8.1 ℓ
Volume of water that flowed out in 1 min
= 8.1 ÷ 6
= 1.35 ℓ
Volume of water that flowed out of Tap B in 1 min
= 2.7 + 1.35
= 4.05 ℓ
(b)
Duration from 8.14 p.m. to 8.21 p.m. = 7 min
Volume of water that flowed out from 8.14 p.m. to 8.21 p.m.
= 7 x 1.35
= 9.45 ℓ
Volume of water left at 8.21 p.m.
= 13.5 - 9.45
= 4.05 ℓ
Fraction of the tank filled with water at 8.21 p.m.
=
4.0527 =
320
Answer(s): (a) 4.05 ℓ; (b) 320