A rectangular tank measuring 77 cm by 54 cm by 32 cm was to be filled with water by two taps, A and B. Tap A which fills the tank at a rate of 9 ℓ per minute was first turned on for 4 minutes before Tap B was turned on as well. If the tank was filled to the brim in a total of 6 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 tank
= 77 x 54 x 32
= 133056 cm
3 1 ℓ = 1000 cm
3 9 ℓ = 9000 cm
3 Volume of water filled by Tap A
= 9000 x 6
= 54000 cm
3 Volume of water filled by Tap B
= 133056 - 54000
= 79056 cm
3 Rate in which Tap B fills the tank
= 79056 ÷ 2
= 39528 cm3/min
39528 mℓ/min
= 39.528 ℓ/min
≈ 39.5 ℓ/min (Correct to 1 decimal place)
Answer(s): 39.5 ℓ/min