21). There is a crack at the bottom of a tank. Before the crack appeared, Pipe A could fill the tank in 2 hours. Now it takes half an hour longer. How long will the crack take to empty a full tank when Pipe A is kept closed?
A). 10 hours 
B). 12 hours 
C). 15 hours 
D). 9 hours 

22). Pipe A can fill a tank in 14 hours and Pipe B can fill the same tank in 16 hours. Because of a crack at the bottom of the tank, it takes 32 minutes more to fill the empty tank when both the pipes are kept open simultaneously. How long will the crack at the bottom take to drain a full tank if Pipes A and B are kept closed?
A). 108 hours 
B). 112 hours 
C). 120 hours 
D). 130 hours 

23). 3 small pumps and a large pump are filling a tank. Each of the three small pumps works at 2/3rd the rate of the large pump. If all 4 pumps work together, they should fill the tank in what fraction of the time that would have taken the large pump alone?
A). \( \Large \frac{1}{5} \)th of the time 
B). \( \Large \frac{1}{4} \)th of the time 
C). \( \Large \frac{1}{3} \)rd of the time 
D). \( \Large \frac{1}{6} \)th of the time 

24). Pipe A which can fill a tank in 20 minutes is kept open for 5 minutes when the tank is empty. Then Pipe B which can fill the tank in 30 minutes is also opened. How long after Pipe A is opened will the tank be full?
A). 12 minutes 
B). 17 minutes 
C). 16 minutes 
D). 14 minutes 

25). Pipe A alone can fill a tank in 8 minutes. Pipe B alone can fill the same tank in 12 minutes. Both the pipes are opened together when the tank is empty. However, Pipe B is closed 3 minutes before the tank is full. In what time did the tank get filled?
A). 6 minutes 
B). 8 minutes 
C). 10 minutes 
D). 12 minutes 

26). Pipe A alone can fill a tank in 12 minutes and Pipe B can fill the same tank in 15 minutes. Pipe C which is at the bottom of the tank can drain the tank at the rate of 22 litres/minute. If all three pipes are kept open together when the tank is full, the tank gets emptied in one hour. What is the capacity of the tank?
A). 140Ltrs. 
B). 132 Ltrs. 
C). 150 Ltrs. 
D). 146 Ltrs. 

27). Pipe A can fill a tank in 4 minutes. Pipe B can fill the same tank in 8 minutes. Pipe C at the bottom of the tank can drain the tank completely in 6 minutes. If all three pipes are kept open together when the tank is empty and pipe C is shut after 3 minutes, in how many minutes will the tank be full after Pipe C is shut?
A). 3 minutes 
B). 5 minutes 
C). 1 minute 
D). 2 minutes 

28). Pipe A fills a tank in 24 minutes. Pipe B can fill the same tank 7 times as fast as Pipe A. If both the pipes are kept open when the tank is empty, when will the tank be full?
A). 5 minutes 
B). 2 minutes 
C). 4 minutes 
D). 3 minutes 

29). Pipe A can fill a tank in 10 minutes. Pipe B can fill the same tank in 15 minutes. Pipe C at the bottom of the tank is a waste pipe for emptying the tank. After opening Pipe A and Pipe B, a man returns when the tank should have been full. However, he finds that Pipe C was also kept open and shuts it and the tank overflows in the next 2 minutes. How many minutes will Pipe C take to empty the tank if Pipes A and B are kept shut?
A). 18 minutes 
B). 16 minutes 
C). 14 minutes 
D). 12 minutes 

30). A tank is fitted with 8 pipes, some that fill the tank and others that empty the tank. Each of the fill pipes fills the tank in 8 hours, while each of the waste pipes empties it in 6 hours. lf all the pipes are kept open when the tank is full, the tank will be completely drained in 6 hours. How many of these 8 pipes are fill pipes?
A). 6 fill pipes 
B). 4 fill pipes 
C). 7 fill pipes 
D). 3 fill pipes 
