The figure shows an empty rectangular tank with a capacity of 39 ℓ. The tank has a height of 30 cm. Tap Q filled the tank at a rate of 3 ℓ per minute. Tap R drained water from the tank at a rate of 1.8 ℓ per minute. Both taps were turned on for 11 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
39 ℓ = 39 x 1000 = 39000 mℓ
Base area of the tank
=
Volumeheight =
3900030 = 1300 cm
2 (b)
Volume of water that filled the tank per minute when both taps were turned on
= 3 - 1.8
= 1.2 ℓ
Volume of water that filled the tank in 11 minutes when both taps were turned on
= 11 x 1.2
= 13.2 ℓ
Volume of water needed to fill the tank
= 39 - 13.2
= 25.8 ℓ
Answer(s): (a) 1300 cm
2; (b) 25.8 ℓ