PSLE The figure shows taps A and B and an empty tank. At 2 p.m., tap A was turned on. Water flowed into the tank from tap A at a rate of 3.6 litres per minute. After 6 minutes, tap B was turned on. At 2.12 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 2.22 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 2.12 p.m. when it was half filled with water
= 42 ÷ 2
= 21 ℓ
Volume of water by Tap A for 6 min
= 6 x 3.6
= 21.6 ℓ
Duration that Tap B was turned
= 12 - 6
= 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
= 21.6 - 21
= 0.6 ℓ
Volume of water that flowed out in 1 min
= 0.6 ÷ 6
= 0.1 ℓ
Volume of water that flowed out of Tap B in 1 min
= 3.6 + 0.1
= 3.7 ℓ
(b)
Duration from 2.12 p.m. to 2.22 p.m. = 10 min
Volume of water that flowed out from 2.12 p.m. to 2.22 p.m.
= 10 x 0.1
= 1 ℓ
Volume of water left at 2.22 p.m.
= 21 - 1
= 20 ℓ
Fraction of the tank filled with water at 2.22 p.m.
=
2042 =
1021
Answer(s): (a) 3.7 ℓ; (b) 1021