Question : Pipes A, B and C can fill a tank in 10, 15 and 30 hours, respectively. D is an emptying pipe which alone can empty the full tank in $x$ hours. A, B and C are opened together for 3 hours and then closed. Now D is opened which alone empties the tank in 30 hours. What is the value of $x$?

Option 1: 50

Option 2: 40

Option 3: 60

Option 4: 45

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 an empty tank in 6 and 8 hours respectively, while pipe C can empty the full tank in 10 hours. If all three pipes are opened together, then the tank will get filled in:

Option 1: $4 \frac{4}{23}$ hours

Option 2: $6\frac{1}{5}$ hours

Option 3: $5\frac{5}{23}$ hours

Option 4: $7\frac{1}{2}$ hours

Question : Pipes A and B can empty a full tank in 18 hours and 24 hours, respectively. Pipe C alone can fill the tank in 36 hours. If the tank is $\frac{5}{6}$ full and all the three pipes are opened together, then in how many hours will the tank be emptied?

Option 1: $10 \frac{1}{2}$

Option 2: $12 \frac{1}{2}$

Option 3: $10$

Option 4: $12$

Question : Pipes A and B can fill a tank in 16 hours and 24 hours, respectively, whereas pipe C can empty the full tank in 40 hours. All three pipes are opened together, but pipe C is closed after 10 hours. After how many hours will the remaining part of the tank be filled?

Option 1: $2 \frac{1}{2}$

Option 2: $2$

Option 3: $5 \frac{1}{2}$

Option 4: $5$