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- Half of the water tank is filled manually.
Question 1:
Half of the water tank is filled manually. Tap A can fill the tank in 20 minutes and B can empty the tank in 12 minutes. If A and B are opened together,then the time taken to empty or fill the tank is:
A. 30 minutes
B. 15/2 minutes
Feedback Given that, A takes 20 minutes to fill and B takes 12 minutes to empty.
Clearly, tap B is faster than tap A. And so, the tank will be emptied.
Half of the tank or 1/2 part of the tank is already filled.
Therefore, we have to find the time taken to empty that 1/2 part.
Part filled by A in 1 minute = 1/20
Part emptied by B in 1 minute = 1/12.
Part emptied by (A+B) in 1 minute = 1/12 – 1/20 = (5-3)/60 = 2/30.
Therefore, time taken by (A+B) to empty the full tank is 15 minutes.
Time taken to empty 1/2 part of the tank is 30/2 = 15/2 minutes.
Clearly, tap B is faster than tap A. And so, the tank will be emptied.
Half of the tank or 1/2 part of the tank is already filled.
Therefore, we have to find the time taken to empty that 1/2 part.
Part filled by A in 1 minute = 1/20
Part emptied by B in 1 minute = 1/12.
Part emptied by (A+B) in 1 minute = 1/12 – 1/20 = (5-3)/60 = 2/30.
Therefore, time taken by (A+B) to empty the full tank is 15 minutes.
Time taken to empty 1/2 part of the tank is 30/2 = 15/2 minutes.
C. 60 minutes
D. 45/2 minutes
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