An empty rectangular container has a capacity of 75 ℓ and a height of 40 cm. At 7 a.m., Tap C is turned on to fill the container at a rate of 6 ℓ per minute for 15 minutes. After 6 minutes, Tap D is turned on to drain water from the container at a rate of 3 ℓ per minute for 11 minutes. What is the height of the water level in the container in the end? Give the answer in 1 decimal place.
1 ℓ = 1000 cm³ 
6 ℓ = 6000 cm³ 
3 ℓ = 3000 cm³ 
75 ℓ = 75000 cm³

Volume of water flowed in from Tap C
= 15 x 6000
= 90000 cm³

Volume of water from drained from Tap D
= 11 x 3000
= 33000 cm³

Volume of water left in the container
= 90000 - 33000
= 57000 cm³

Base area of the container
= 75000 ÷ 40
= 1875 cm² 

Height of water left in the container
= 57000 ÷ 1875
≈ 30.4 cm

Answer(s): 30.4 cm