An empty rectangular tank has a capacity of 91 ℓ and a height of 50 cm. At 8 a.m., Tap Y is turned on to fill the tank at a rate of 10 ℓ per minute for 18 minutes. After 3 minutes, Tap Z is turned on to drain water from the tank at a rate of 4 ℓ per minute for 23 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 
10 ℓ = 10000 cm³ 
4 ℓ = 4000 cm³ 
91 ℓ = 91000 cm³

Volume of water flowed in from Tap Y
= 18 x 10000
= 180000 cm³

Volume of water from drained from Tap Z
= 23 x 4000
= 92000 cm³

Volume of water left in the tank
= 180000 - 92000
= 88000 cm³

Base area of the tank
= 91000 ÷ 50
= 1820 cm² 

Height of water left in the tank
= 88000 ÷ 1820
≈ 48.4 cm

Answer(s): 48.4 cm