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 3.3 litres per minute. After 8 minutes, tap B was turned on. At 5.14 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 5.20 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 5.14 p.m. when it was half filled with water
= 42 ÷ 2
= 21 ℓ
Volume of water by Tap A for 8 min
= 8 x 3.3
= 26.4 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
= 26.4 - 21
= 5.4 ℓ
Volume of water that flowed out in 1 min
= 5.4 ÷ 6
= 0.9 ℓ
Volume of water that flowed out of Tap B in 1 min
= 3.3 + 0.9
= 4.2 ℓ
(b)
Duration from 5.14 p.m. to 5.20 p.m. = 6 min
Volume of water that flowed out from 5.14 p.m. to 5.20 p.m.
= 6 x 0.9
= 5.4 ℓ
Volume of water left at 5.20 p.m.
= 21 - 5.4
= 15.6 ℓ
Fraction of the tank filled with water at 5.20 p.m.
=
15.642 =
1335
Answer(s): (a) 4.2 ℓ; (b) 1335