A rectangular tank measuring 85 cm by 52 cm by 28 cm was to be filled with water by two taps, R and S. Tap R which fills the tank at a rate of 8 ℓ per minute was first turned on for 2 minutes before Tap S was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap R was first turned on, what is the rate at which Tap S fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the tank
= 85 x 52 x 28
= 123760 cm³ 

1 ℓ = 1000 cm³ 
8 ℓ = 8000 cm³ 

Volume of water filled by Tap R
= 8000 x 7
= 56000 cm³

Volume of water filled by Tap S
= 123760 - 56000
= 67760 cm³ 

Rate in which Tap S fills the tank
= 67760 ÷ 5
13552 mℓ/min
= 13.552 ℓ/min
≈ 13.6 ℓ/min (Correct to 1 decimal place)

Answer(s): 13.6 ℓ/min