An empty rectangular container has a capacity of 21 ℓ and a height of 20 cm. At 6 a.m., Tap H is turned on to fill the container at a rate of 10 ℓ per minute for 16 minutes. After 4 minutes, Tap J is turned on to drain water from the container at a rate of 3 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 
10 ℓ = 10000 cm³ 
3 ℓ = 3000 cm³ 
21 ℓ = 21000 cm³

Volume of water flowed in from Tap H
= 16 x 10000
= 160000 cm³

Volume of water from drained from Tap J
= 23 x 3000
= 69000 cm³

Volume of water left in the container
= 160000 - 69000
= 91000 cm³

Base area of the container
= 21000 ÷ 20
= 1050 cm² 

Height of water left in the container
= 91000 ÷ 1050
≈ 86.7 cm

Answer(s): 86.7 cm