An empty rectangular container has a capacity of 95 ℓ and a height of 40 cm. At 7 a.m., Tap X is turned on to fill the container at a rate of 9 ℓ per minute for 15 minutes. After 4 minutes, Tap Y is turned on to drain water from the container at a rate of 4 ℓ per minute for 21 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 
9 ℓ = 9000 cm³ 
4 ℓ = 4000 cm³ 
95 ℓ = 95000 cm³

Volume of water flowed in from Tap X
= 15 x 9000
= 135000 cm³

Volume of water from drained from Tap Y
= 21 x 4000
= 84000 cm³

Volume of water left in the container
= 135000 - 84000
= 51000 cm³

Base area of the container
= 95000 ÷ 40
= 2375 cm² 

Height of water left in the container
= 51000 ÷ 2375
≈ 21.5 cm

Answer(s): 21.5 cm