An empty rectangular tank has a capacity of 139 ℓ and a height of 20 cm. At 7 a.m., Tap Z is turned on to fill the tank at a rate of 2 ℓ per minute for 17 minutes. After 5 minutes, Tap A is turned on to drain water from the tank at a rate of 3 ℓ per minute for 9 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 
2 ℓ = 2000 cm³ 
3 ℓ = 3000 cm³ 
139 ℓ = 139000 cm³

Volume of water flowed in from Tap Z
= 17 x 2000
= 34000 cm³

Volume of water from drained from Tap A
= 9 x 3000
= 27000 cm³

Volume of water left in the tank
= 34000 - 27000
= 7000 cm³

Base area of the tank
= 139000 ÷ 20
= 6950 cm² 

Height of water left in the tank
= 7000 ÷ 6950
≈ 1 cm

Answer(s): 1 cm