There is a water tank which water of 72L is in and water flows into this tank by 3L a minute.
When water is pumped out of this tank with one pump, all water in this tank is pumped out in 24 minutes.
Because water decreases 3L a minute though 3L water flows into the tank, water is pumped out by 6L (3L + 3L = 6L) a minute.
Thus, since 6L water is pumped out by one pump, 12L (6L × 2 = 12L) water is pumped out by two pump.
When 3L water flowing in and 12L water is being pumped out, water decreases by 9L(12L- 3L = 9L) a minute.
Therefore, all water is pumped out in 8 minutes (72 / 9 = 8).
When water is pumped out of this tank with one pump, all water in this tank is pumped out in 24 minutes.
Answer
Eight minutes
Solution
Because all water pumped out in 24 minutes with one pump, water in the tank decreases by 3L (72 / 24 =3) for one minute.
Because water decreases 3L a minute though 3L water flows into the tank, water is pumped out by 6L (3L + 3L = 6L) a minute.
Thus, since 6L water is pumped out by one pump, 12L (6L × 2 = 12L) water is pumped out by two pump.
When 3L water flowing in and 12L water is being pumped out, water decreases by 9L(12L- 3L = 9L) a minute.
Therefore, all water is pumped out in 8 minutes (72 / 9 = 8).
