The figure shows an empty rectangular tank with a capacity of 72 ℓ. The tank has a height of 24 cm. Tap D filled the tank at a rate of 2.5 ℓ per minute. Tap E drained water from the tank at a rate of 1.4 ℓ per minute. Both taps were turned on for 30 minutes and then turned off.
- What is the base area of the tank?
- After both taps were turned off, how much more water is needed to fill the tank completely? Give your answer in litres.
(a)
1 ℓ = 1000 mℓ
72 ℓ = 72 x 1000 = 72000 mℓ
Base area of the tank
=
Volumeheight =
7200024 = 3000 cm
2 (b)
Volume of water that filled the tank per minute when both taps were turned on
= 2.5 - 1.4
= 1.1 ℓ
Volume of water that filled the tank in 30 minutes when both taps were turned on
= 30 x 1.1
= 33 ℓ
Volume of water needed to fill the tank
= 72 - 33
= 39 ℓ
Answer(s): (a) 3000 cm
2; (b) 39 ℓ