PSLE The figure shows taps A and B and an empty tank. At 5 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 5.13 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 5.30 p.m., what fraction of the tank was filled with water?
(a)
Volume of the tank
= 60 x 30 x 20
= 36000 mℓ
= 36 ℓ
Volume of the tank at 5.13 p.m. when it was half filled with water
= 36 ÷ 2
= 18 ℓ
Volume of water by Tap A for 8 min
= 8 x 2.7
= 21.6 ℓ
Duration that Tap B was turned
= 13 - 8
= 5 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 5 min
= 21.6 - 18
= 3.6 ℓ
Volume of water that flowed out in 1 min
= 3.6 ÷ 5
= 0.72 ℓ
Volume of water that flowed out of Tap B in 1 min
= 2.7 + 0.72
= 3.42 ℓ
(b)
Duration from 5.13 p.m. to 5.30 p.m. = 17 min
Volume of water that flowed out from 5.13 p.m. to 5.30 p.m.
= 17 x 0.72
= 12.24 ℓ
Volume of water left at 5.30 p.m.
= 18 - 12.24
= 5.76 ℓ
Fraction of the tank filled with water at 5.30 p.m.
=
5.7636 =
425
Answer(s): (a) 3.42 ℓ; (b) 425