Discussion :: Pipes and Cistern
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How much time will the leak take to empty the full cistern?
I.
The cistern is normally filled in 9 hours.
II.
It takes one hour more than the usual time to fill the cistern because of la leak in the bottom.
A.
I alone sufficient while II alone not sufficient to answer |
B.
II alone sufficient while I alone not sufficient to answer |
C.
Either I or II alone sufficient to answer |
D.
Both I and II are not sufficient to answer |
E.
Both I and II are necessary to answer |
Answer : Option E
Explanation :
I. Time taken to fill the cistern without leak = 9 hours.
Part of cistern filled without leak in 1 hour =\(\frac { 1 } { 9 }\)
II. Time taken to fill the cistern in presence of leak = 10 hours.
Net filling in 1 hour =\(\frac { 1 } {10 }\)
Work done by leak in 1 hour =[\(\frac { 1 } { 9 }\)-\(\frac { 1 } {10 }\)]=\(\frac { 1 } {90 }\)
Leak will empty the full cistern in 90 hours.
Clearly, both I and II are necessary to answer the question.
Correct answer is (E).
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