PSLE The figure shows taps A and B and an empty tank. At 6 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 6 minutes, tap B was turned on. At 6.14 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 6.27 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 6.14 p.m. when it was half filled with water
= 36 ÷ 2
= 18 ℓ
Volume of water by Tap A for 6 min
= 6 x 4.5
= 27 ℓ
Duration that Tap B was turned
= 14 - 6
= 8 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 8 min
= 27 - 18
= 9 ℓ
Volume of water that flowed out in 1 min
= 9 ÷ 8
= 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 6.14 p.m. to 6.27 p.m. = 13 min
Volume of water that flowed out from 6.14 p.m. to 6.27 p.m.
= 13 x 1.125
= 14.625 ℓ
Volume of water left at 6.27 p.m.
= 18 - 14.625
= 3.375 ℓ
Fraction of the tank filled with water at 6.27 p.m.
=
3.37536 =
332
Answer(s): (a) 5.625 ℓ; (b) 332