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 4.5 litres per minute. After 8 minutes, tap B was turned on. At 5.12 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 35 x 30
= 63000 mℓ
= 63 ℓ
Volume of the tank at 5.12 p.m. when it was half filled with water
= 63 ÷ 2
= 31.5 ℓ
Volume of water by Tap A for 8 min
= 8 x 4.5
= 36 ℓ
Duration that Tap B was turned
= 12 - 8
= 4 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 4 min
= 36 - 31.5
= 4.5 ℓ
Volume of water that flowed out in 1 min
= 4.5 ÷ 4
= 1.125 ℓ
Volume of water that flowed out of Tap B in 1 min
= 4.5 + 1.125
= 5.625 ℓ
(b)
Duration from 5.12 p.m. to 5.30 p.m. = 18 min
Volume of water that flowed out from 5.12 p.m. to 5.30 p.m.
= 18 x 1.125
= 20.25 ℓ
Volume of water left at 5.30 p.m.
= 31.5 - 20.25
= 11.25 ℓ
Fraction of the tank filled with water at 5.30 p.m.
=
11.2563 =
528
Answer(s): (a) 5.625 ℓ; (b) 528