PSLE Water could flow out of a tank through tap A and tap B. At first, Bobby turned on tap A. After some time, he also turned on tap B so that more water flowed out. Later, he turned off both taps at the same time. The line graph shows the volume of water in the tank from 14 00 to 14 24
- What was the rate of flow of water from tap A in litres per minute?
- How many litres of water flowed out of the tank throughout the period when both taps were turned on?
- What was the rate of flow of water from tap B in litres per minute?
(a)
Volume of the tank
At 14 00: 115 ℓ
At 14 06: 112 ℓ
At 14 12: 109 ℓ
At 14 18: 100 ℓ
At 14 24: 100 ℓ
Only Tap A was turned on from 14 00 to 14 12.
Decrease in the volume of water from 14 00 to 14 12
= 115 - 109
= 6 ℓ
Rate of flow of water from Tap A
= 6 ÷ 6
= 1 ℓ /min
(b)
Both taps were turned off at 14 18.
Volume of water that flowed out when both taps were turned on
= 109 - 100
= 9 ℓ
(c)
Tap A and Tap B were turned on from 14 12 to 14 18 for a duration of 6 min.
Volume of water that flowed out from Tap A in 6 min
= 6 x 1
= 6 ℓ
Volume of water that flowed out from Tap B in 6 min
= 6 - 9
= -3 ℓ
Rate of water from Tap B
= -3 ÷ 6
= -0.5 ℓ/min
Answer(s): (a) 0.5 ℓ/min; (b) 12 ℓ ; (c) -0.5 ℓ/min