PSLE
Asher filled a tank with water using two taps. He turned on Tap R first and after 6 minutes, he also turned on Tap S. Both taps were turned off at the same time when the tank was completely filled without overflowing. The graph shows the amount of water in the tank over 24 minutes.

1. What fraction of the tank was filled 6 minutes after Tap R was turned on? Express your answer in the simplest form.
2. In one minute, how many litres of water flowed from Tap S?

(a)
Capacity of the tank = 30 ℓ
Volume of water in the tank after 6 minutes = 3 ℓ

Fraction of the tank that was filled 6 minutes after Tap R was turned on
= ³₃₀  
= ¹₁₀

(b) 

	Tap R	Tap S	Total
First 6 min	3 ℓ	0 ℓ	3 ℓ
Next 9 min	4.5 ℓ	22.5 ℓ	27 ℓ

Volume of water that flowed from Tap R and Tap S in 15 minutes = 30 ℓ

Duration that Tap S was turned on
= 15 - 6
= 9 min

Volume of water that flowed from Tap R in 9 minutes
= ³₆  x 9
= 4.5 ℓ

Volume of water that flowed from Tap R and Tap S in 9 minutes
= 30 - 3
= 27 ℓ

Volume of water that flowed from Tap S in 9 minutes
= 27 - 4.5
= 22.5 ℓ

Volume of water that flowed from Tap S in 1 minute
= 22.5 ÷ 9
= 2.5 ℓ

Answer(s): (a) ¹₁₀ ; (b) 2.5 ℓ