An empty rectangular container has a capacity of 84 ℓ and a height of 10 cm. At 10 a.m., Tap R is turned on to fill the container at a rate of 8 ℓ per minute for 18 minutes. After 11 minutes, Tap S is turned on to drain water from the container at a rate of 2 ℓ per minute for 23 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 
8 ℓ = 8000 cm³ 
2 ℓ = 2000 cm³ 
84 ℓ = 84000 cm³

Volume of water flowed in from Tap R
= 18 x 8000
= 144000 cm³

Volume of water from drained from Tap S
= 23 x 2000
= 46000 cm³

Volume of water left in the container
= 144000 - 46000
= 98000 cm³

Base area of the container
= 84000 ÷ 10
= 8400 cm² 

Height of water left in the container
= 98000 ÷ 8400
≈ 11.7 cm

Answer(s): 11.7 cm