Question : Two pipes A and B can fill a tank in 12 hours and 18 hours, respectively. Both pipes are opened simultaneously. In how much time will the empty tank be filled completely?

Option 1: 9 hours 30 minutes

Option 2: 8 hours

Option 3: 7 hours 12 minutes

Option 4: 10 hours 24 minutes

Question : Pipes A, B and C together can fill a cistern in 12 hours. All three pipes are opened together for 4 hours and then C is closed. A and B together take 10 hours to fill the remaining part of the cistern. C alone will fill two-thirds of the cistern in:

Option 1: 60 hours

Option 2: 40 hours

Option 3: 48 hours

Option 4: 50 hours

Question : Two inlet pipes can fill a cistern in 10 and 12 hours respectively and an outlet pipe can empty 80 gallons of water per hour. All three pipes working together can fill the empty cistern in 20 hours. What is the capacity (in gallons) of the tank?

Option 1: 360

Option 2: 300

Option 3: 600

Option 4: 900

Question : Two pipes can fill a tank in 15 hours and 4 hours, respectively, while a third pipe can empty it in 12 hours. How long (in hours) will it take to fill the empty tank if all three pipes are opened simultaneously?

Option 1: $\frac{50}{7}$

Option 2: $\frac{15}{7}$

Option 3: $\frac{30}{7}$

Option 4: $\frac{20}{7}$

Question : Pipes A and B can fill a tank in 18 minutes and $22 \frac{1}{2}$ minutes, respectively while pipe C can empty the full tank in 12 minutes. A and B are opened together for 6 minutes and then closed. Now C is opened. C alone will empty the tank in ____.

Option 1: $5$ minutes

Option 2: $8 \frac{2}{5}$ minutes

Option 3: $7 \frac{1}{5}$ minutes

Option 4: $6$ minutes