Answer:
a) 9000 L


c) Proof below.

e) 5 hours 23 minutes
Explanation:
Part (a)
The aquarium can be modeled as a rectangular prism.
Note: 1 m³ = 1000 L

Part (b)



Part (c)
4 hours = 4 × 60 minutes = 240 minutes
If it takes 4 hours longer to fill the aquarium with water using tap P as compared to tap Q, then:

Part (d)
Quadratic Formula

Therefore:

Substitute these values into the formula and solve for x:







As the rate is positive only,

Part (e)
If the rate that tap P fills the aquarium with water is x litres per min, and the rate the tap Q fills the aquarium with water is (x+5) litres per min, the rate that both taps fill the aquarium is:

Therefore, if both taps are turned on together, the time it takes to fill the 9000L aquarium is:




Note we really should round up to the nearest minute, even though 23.289... rounded is 23, as if we round down, the aquarium will not quite be filled with water.