An empty rectangular tank has a capacity of 63 ℓ and a height of 20 cm. At 6 a.m., Tap F is turned on to fill the tank at a rate of 7 ℓ per minute for 16 minutes. After 8 minutes, Tap G is turned on to drain water from the tank at a rate of 5 ℓ per minute for 18 minutes. What is the height of the water level in the tank in the end? Give the answer in 1 decimal place.
1 ℓ = 1000 cm³ 
7 ℓ = 7000 cm³ 
5 ℓ = 5000 cm³ 
63 ℓ = 63000 cm³

Volume of water flowed in from Tap F
= 16 x 7000
= 112000 cm³

Volume of water from drained from Tap G
= 18 x 5000
= 90000 cm³

Volume of water left in the tank
= 112000 - 90000
= 22000 cm³

Base area of the tank
= 63000 ÷ 20
= 3150 cm² 

Height of water left in the tank
= 22000 ÷ 3150
≈ 7 cm

Answer(s): 7 cm