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 2.7 litres per minute. After 7 minutes, tap B was turned on. At 6.11 p.m., the tank was half filled with water.
- How many litres of water flowed out of tap B in 1 minute?
- At 6.23 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 6.11 p.m. when it was half filled with water
= 36 ÷ 2
= 18 ℓ
Volume of water by Tap A for 7 min
= 7 x 2.7
= 18.9 ℓ
Duration that Tap B was turned
= 11 - 7
= 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
= 18.9 - 18
= 0.9 ℓ
Volume of water that flowed out in 1 min
= 0.9 ÷ 4
= 0.225 ℓ
Volume of water that flowed out of Tap B in 1 min
= 2.7 + 0.225
= 2.925 ℓ
(b)
Duration from 6.11 p.m. to 6.23 p.m. = 12 min
Volume of water that flowed out from 6.11 p.m. to 6.23 p.m.
= 12 x 0.225
= 2.7 ℓ
Volume of water left at 6.23 p.m.
= 18 - 2.7
= 15.3 ℓ
Fraction of the tank filled with water at 6.23 p.m.
=
15.336 =
1740
Answer(s): (a) 2.925 ℓ; (b) 1740