Mathematics
NULL
Medium
Question
A cistern that fills in 9 hours takes one hour more because of a leak. If full, in what time will the leak empty it?
A
45 hrs
B
60 hrs
C
75 hrs
D
90 hrs
✓ Official correct answer
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A
45 hrs
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B
60 hrs
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C
75 hrs
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D
90 hrs
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Explanation
Leak rate = 1/9 − 1/10 = 1/90. Emptying time = 90 hrs.