A rectangular container measuring 81 cm by 51 cm by 20 cm was to be filled with water by two taps, F and G. Tap F which fills the tank at a rate of 7 ℓ per minute was first turned on for 2 minutes before Tap G was turned on as well. If the tank was filled to the brim in a total of 6 minutes from the time when Tap F was first turned on, what is the rate at which Tap G fills the tank? Give your answer in ℓ per minute correct to 1 decimal place.
Total volume of the container
= 81 x 51 x 20
= 82620 cm
3 1 ℓ = 1000 cm
3 7 ℓ = 7000 cm
3 Volume of water filled by Tap F
= 7000 x 6
= 42000 cm
3 Volume of water filled by Tap G
= 82620 - 42000
= 40620 cm
3 Rate in which Tap G fills the container
= 40620 ÷ 4
= 10155 cm3/min
10155 mℓ/min
= 10.155 ℓ/min
≈ 10.2 ℓ/min (Correct to 1 decimal place)
Answer(s): 10.2 ℓ/min