A rectangular tank measuring 74 cm by 52 cm by 22 cm was to be filled with water by two taps, R and S. Tap R which fills the tank at a rate of 7 ℓ per minute was first turned on for 3 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
= 74 x 52 x 22
= 84656 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap R
= 7000 x 7
= 49000 cm
3 Volume of water filled by Tap S
= 84656 - 49000
= 35656 cm
3 Rate in which Tap S fills the tank
= 35656 ÷ 4
= 8914 cm3/min
8914 mℓ/min
= 8.914 ℓ/min
≈ 8.9 ℓ/min (Correct to 1 decimal place)
Answer(s): 8.9 ℓ/min