A rectangular container measuring 81 cm by 58 cm by 20 cm was to be filled with water by two taps, A and B. Tap A which fills the tank at a rate of 5 ℓ per minute was first turned on for 2 minutes before Tap B was turned on as well. If the tank was filled to the brim in a total of 7 minutes from the time when Tap A was first turned on, what is the rate at which Tap B fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the container
= 81 x 58 x 20
= 93960 cm
3 1 ℓ = 1000 cm
3 5 ℓ = 5000 cm
3 Volume of water filled by Tap A
= 5000 x 7
= 35000 cm
3 Volume of water filled by Tap B
= 93960 - 35000
= 58960 cm
3 Rate in which Tap B fills the container
= 58960 ÷ 5
= 11792 cm3/min
11792 mℓ/min
= 11.792 ℓ/min
≈ 11.8 ℓ/min (Correct to 1 decimal place)
Answer(s): 11.8 ℓ/min