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 3.9 litres per minute. After 6 minutes, tap B was turned on. At 5.15 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 5.24 p.m., what fraction of the tank was filled with water?
(a)
Volume of the tank
= 60 x 30 x 25
= 45000 mℓ
= 45 ℓ
Volume of the tank at 5.15 p.m. when it was half filled with water
= 45 ÷ 2
= 22.5 ℓ
Volume of water by Tap A for 6 min
= 6 x 3.9
= 23.4 ℓ
Duration that Tap B was turned
= 15 - 6
= 9 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 9 min
= 23.4 - 22.5
= 0.9 ℓ
Volume of water that flowed out in 1 min
= 0.9 ÷ 9
= 0.1 ℓ
Volume of water that flowed out of Tap B in 1 min
= 3.9 + 0.1
= 4 ℓ
(b)
Duration from 5.15 p.m. to 5.24 p.m. = 9 min
Volume of water that flowed out from 5.15 p.m. to 5.24 p.m.
= 9 x 0.1
= 0.9 ℓ
Volume of water left at 5.24 p.m.
= 22.5 - 0.9
= 21.6 ℓ
Fraction of the tank filled with water at 5.24 p.m.
=
21.645 =
1225
Answer(s): (a) 4 ℓ; (b) 1225