Pipes and Cistern
 Pipe A can fill a tank in 45 hrs and pipe B can fill it in 36 hrs. If both the pipes are opened in the empty tank. In how many hours will it be full?

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Part filled by A in 1 hr= (1/45)
Part filled by B in 1 hr= (1/36)Correct Option: C
Part filled A in 1 hr= (1/45)
Part filled B in 1 hr= (1/36)
Part filled by (A+B) together in 1 hr=(1/45)+(1/36)=1/20
So, The tank will be full in 20 hr.
 If a pipe fills a tank in 6 h, then what part of the tank will the pipe fill in 1 h?

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We know that, when a pipe fills a tank in m h, then the part of tank filled in 1 h = 1/m
Correct Option: B
We know that, when a pipe fills a tank in m h, then the part of tank filled in 1 h = 1/m
Here, m = 6
∴ Required part of the tank to be filled in 1h = 1/6 part
 A cistern is normally filled in 8 hours but takes two hours longer to fill because of a leak in its bottom. If the cistern is full, the leak will empty it in ?

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Work done by leak in 1 hour = (1/8  1/10) = 1/40
Correct Option: D
Work done by leak in 1 hour = (1/8  1/10) = 1/40
∴ The leak will empty the cistern in 40 hours.
 A pipe can empty a tank in 12 minutes and another pipe can empty it in 16 minutes. If both the pipes are opened simultaneously, find the time in which a full tank is emptied ?

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Required answer = (12 x 16) /(12 + 16) = 48 / 7 = 6^{6}/_{7} minutes.
Correct Option: D
Required answer = (12 x 16) /(12 + 16) = 48 / 7 = 6^{6}/_{7} minutes.
 A cistern is normally filled in 8 hrs. but takes 2 hrs. longer to fill because of a leak in its bottom. If the cistern is full, the leak will empty it in ?

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Here x = 8 hrs. and y = 8 + 2 = 10 hrs.
Now, applying the given rule, we have the
Required answer = (8 x 10) /(10  8) = 40 hrs.Correct Option: B
Here x = 8 hrs. and y = 8 + 2 = 10 hrs.
Now, applying the given rule, we have the
Required answer = (8 x 10) /(10  8) = 40 hrs.