An empty rectangular tank has a capacity of 70 ℓ and a height of 80 cm. At 6 a.m., Tap V is turned on to fill the tank at a rate of 4 ℓ per minute for 17 minutes. After 2 minutes, Tap W is turned on to drain water from the tank at a rate of 6 ℓ per minute for 10 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 
4 ℓ = 4000 cm³ 
6 ℓ = 6000 cm³ 
70 ℓ = 70000 cm³

Volume of water flowed in from Tap V
= 17 x 4000
= 68000 cm³

Volume of water from drained from Tap W
= 10 x 6000
= 60000 cm³

Volume of water left in the tank
= 68000 - 60000
= 8000 cm³

Base area of the tank
= 70000 ÷ 80
= 875 cm² 

Height of water left in the tank
= 8000 ÷ 875
≈ 9.1 cm

Answer(s): 9.1 cm