An empty rectangular tank has a capacity of 187 ℓ and a height of 11 cm. At 7 a.m., Tap R is turned on to fill the tank at a rate of 10 ℓ per minute for 20 minutes. After 4 minutes, Tap S is turned on to drain water from the tank at a rate of 4 ℓ per minute for 7 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 
187 ℓ = 187000 cm³

Volume of water flowed in from Tap R
= 20 x 10000
= 200000 cm³

Volume of water from drained from Tap S
= 7 x 4000
= 28000 cm³

Volume of water left in the tank
= 200000 - 28000
= 172000 cm³

Base area of the tank
= 187000 ÷ 11
= 17000 cm² 

Height of water left in the tank
= 172000 ÷ 17000
≈ 10.1 cm

Answer(s): 10.1 cm