In 2 minutes, 12 liters of water flow into the bathtub and 2 liters (2 minutes x 1 liter / minute ) escape. This will leave 12 – 2 = 10 liters of water every two minutes. We can divide the number of liters by the number of minutes to find the average flow per minute, which is 10 / 2 = 5 liters per minute. To fill the tub, it will take 120 liters / 5 liters / min = 24 min.
This justifies what answer for what question? Q & A:
Robi Ney wants to fill a 120-liter tub. He is amused by letting the water run for 1 minute, then closing the water supply for 1 minute, and so on alternating opening and closing the water supply. But the cap at the bottom of the tub is not very airtight and lets 1 liter of water escape per minute. The flow rate of the tap is 12 liters per minute. How long does it take to fill the tub in minutes?
24