An empty rectangular tank has a capacity of 114 ℓ and a height of 80 cm. At 10 a.m., Tap X is turned on to fill the tank at a rate of 7 ℓ per minute for 20 minutes. After 11 minutes, Tap Y is turned on to drain water from the tank at a rate of 6 ℓ per minute for 12 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 
6 ℓ = 6000 cm³ 
114 ℓ = 114000 cm³

Volume of water flowed in from Tap X
= 20 x 7000
= 140000 cm³

Volume of water from drained from Tap Y
= 12 x 6000
= 72000 cm³

Volume of water left in the tank
= 140000 - 72000
= 68000 cm³

Base area of the tank
= 114000 ÷ 80
= 1425 cm² 

Height of water left in the tank
= 68000 ÷ 1425
≈ 47.7 cm

Answer(s): 47.7 cm