1.A tank can be filled by two pipes in 20 minutes and 30 minutes respectively. When the tank was empty, the two pipes were opened. After some time, the first pipe was stopped and the tank was filled in 18 minutes. After how much time of the start, was the first pipe stopped?

a) 10 minutes

b) 8 minutes

c) 12 minutes

d) 16 minutes

b

2.A pipe can empty a tank in 15 hours. Another pipe can empty the tank in 10 hours. In how much time will the completely filled tank get emptied if both the pipes are open together?

a) 7 hours

b) 6 hours

c) 8 hours

d) 9 hours

b

3.Pipes A, B, C can fill the tank alone in 10, 15, 20 hours respectively. If all the three pipes are simultaneously opened, in how much time will the tank be full

a) 4 1/3 hours

b) 4 2/3 hours

c) 4 8/13 hours

d) 18 hours

c

4.Pipes A and B can fill a tank alone in 12 and 15 hours respectively. Pipe C can empty the full tank in 18 hours. If all the three pipes are opened simultaneously, how much time it will take them to fill the tank completely.

a) 7 hours

b) 8 hours

c) 10 10/17 hours

d) 18 1/3 hours

c

5.Pipes A and B can fill a tank separately in 36 and 48 hours respectively. Both pipes are opened together to fill the tank. After some time pipe B is closed and the tank is full in 24 hours. For how much time was the pipe B open?

a) 12 hours

b) 14 hours

c) 15 hours

d) 16 hours

d

6.Two pipes A and B can fill a tank in 12 and 15 minutes. Both pipes are opened together but after 3 minutes the first pipe is turned off. How much longer will the tank take to fill?

a) 8 1/3 minutes

b) 9 minutes

c) 10 minutes

d) 8 1/4 minutes

d

7.Pipes A and B can fill a tank in 24 and 30 minutes respectively. An outlet pipe C can empty it in 12 minutes. In the beginning, pipes A and B are opened together and after 10 minutes pipe C is also opened. In how much time will the tank be emptied?

a) 90 minutes

b) 75 minutes

c) 60 minutes

d) 80 minutes

a

8.Pipes A, B, C when opened together, fill the tank in 15 hours. Pipe A alone can fill it in 10 hours, while B alone in 20 hours. How does pipe C work?

a) empty in 12 hours

b) empty in 15 hours

c) full in 18 hours

d) full in 15 hours

a

9.One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill the tank in 36 minutes, the slower pipe alone will be able to fill the tank in

a) 10 minutes

b) 144 minutes

c) 12 minutes

d) None

b

10.Two pipes A and B can fill a water tank in 20 and 24 minutes respectively and a third pipe C can empty at the rate of 3 gallons per minute. If A, B and C opened together fill the tank in 15 minutes, the capacity (in gallons) of the tank is:

a) 220

b) 150

c) 120

d) 140

c