One fill pipe and one emptying pipe open together: time to fill

The same question, asked 2 times: 25 Sep 2024 S1*, 25 Sep 2024 S3. Every wording below, oldest first.

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Question 1
25 Sep 2024 S1
67 $An inlet pipe can fill a water storage tank in 11 hours and an outlet pipe can empty the completely filled tank in 15 hours .If both pipes opened simultaneously. The time taken to fill the empty tank ( in hrs) is :$
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Question 2
25 Sep 2024 S3
53 $A tap can fill a cistern in 10 minutes and another tap can empty it in 12 minutes. If both the taps are open, the time (in hours) taken to fill the tank will be:$
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Question 1